Every heavy industrial manufacturer would agree that the best solution to a maintenance and reliability issue is the most efficient one. One that provides a quality solution, in the ideal amount of time, at a price that fits within the budget. Thermal spray coatings provide wear and corrosion resistant coatings that increase the efficiency of heavy industrial parts. To maximize that efficiency, choosing the right thermal spray provider is paramount. One often overlooked factor is grinding capabilities. Grinding services are a key component of the thermal spray process and can have a profound effect on the coating quality, lead time, and cost of thermal spray coatings.
Thermal spray coatings are applied with a variety of spray methods, and some have more precise coating thicknesses than others. Most of the time, a thermal spray coating is built up thicker than the desired finish dimensions. Grinding or diamond grinding is used to achieve the correct dimensional tolerances and surface finish required for optimal performance. Coatings are sometimes left in the as-sprayed condition to offer friction and grip benefits but may not be as precise of a dimension. So, since grinding is essential, having thermal spray and grinding services under one roof provides some serious benefits.
Most conventional grind shops don’t regularly work with hardened materials. Thermal spray coatings can have hardness measurements of upwards of 50-60 Rockwell C. Grinding tungsten carbide is very different than grinding stainless steel. In fact, grinding a thermal spray stainless steel coating is very different from grinding stainless steel stock material due to the way the coatings are formed. If a thermal spray company has in-house grinding, their grinding operators will have more experience working with hardened coatings. Knowledge and expertise in finish grinding thermal spray coatings can impact coating quality and performance. Experience level can also affect processing speed and lead times.
If you only need to move a part 20 feet versus 20 plus miles after coating, it will save time. Shipping to an outsourced grind shop can add 1-3 weeks, or more, to your turnaround time. You also raise the risk of compounding any backlog the thermal spray provider or grind shop might have. Not only do you have to factor in the added lead time from outsourcing grinding services, but the added cost as well.
I’m going to let you in on a little industry secret, most companies have to up-charge any outsourced services to cover the cost of shipping and the added liability of things going wrong when the parts are at another vendor. The cost of the grinding service itself will also be higher since the outsourced grinding provider will add their profit markup as well. Using a thermal spray company that has in-house grinding capabilities will reduce the cost of a thermal spray coating.
Most people choose thermal spray coatings to increase the efficiency of their product or process. For a thermal spray solution to be efficient it will provide good coating quality, lead time, and cost. All of that to say, there’s a time and a place to outsource grinding. We do it, from time to time, if the part is too large for our equipment or requires a more advanced type of grinding technique. However, the benefits of in-house grinding services for everyday diamond grinding and cylindrical grinding are clear. To get the most out of your thermal spray coatings choose a thermal spray company that has in-house grinding capabilities.
In the ever-changing landscape of glass container manufacturing, the pursuit of efficiency and durability is ongoing. One transformative technology making a significant impact is thermal spray coatings. Thermal spray coatings are used in many different areas of the glass container manufacturing process, from molds to conveyor shafts. The most frequent use is to protect and maintain deflectors and scoops. Thermal spray helps mitigate wear and tear from heat and high-volume use. So, what is thermal spray, how does it work, and what are its benefits for deflectors and scoops? Let’s start at the beginning…
Thermal spray is a coating process that applies semi-molten metal to a substrate, kind of like spray painting with molten metal. There are various thermal spray processes, but they all use either a powder or wire material to apply specialized coatings such as nickel graphite, tungsten carbide, and many more. It has a relatively low application temperature compared to other coating types, such as laser cladding or welding, so parts are not distorted during the application process. For some coatings, this makes it possible to apply thermal spray coatings repeatedly, as needed, to the same parts.
For a more in-depth look at Thermal Spray, check out Thermal Spray 101
Thermal spray coatings can be applied to new or used deflectors. If parts are used, the parts are first degreased, and any prior coating is removed. The parts are then mounted, and the thermal spray coating is robotically applied. Finally, they are polished smooth, and ready to be put back into production. As simple as the process seems, these coatings can have profound results for the glass container manufacturing industry. The carbide coating used on scoops is very durable and, therefore, hard to remove so it can only be applied to new scoops.
One of the standout advantages of thermal spray in glass container manufacturing is its ability to resist wear and corrosion. These coatings extend the life of manufacturing components and reduce maintenance downtime. When components last longer it also minimizes replacement costs and reduces overall maintenance expenses. Thermal spray can be used, in some cases, to reclaim worn parts instead of purchasing new ones.
Deflectors and scoops see temperatures upwards of 2000 °F. The addition of heat to an already abrasive environment increases part erosion. Thermal spray coatings can act as a heat barrier between the glass glob and the underlying base material, extending the life of the parts.
The biggest improvement we have seen thermal spray coating bring to the glass container manufacturing industry is lubrication. Due to the natural material properties and the porosity of the coating, which holds onto swabbing lubricants, we have seen deflectors stay in production 2-3 times longer than swabbing alone.
Thermal spray coatings are beneficial across many industries and glass container manufacturing is no different. While many components in glass container production benefit from thermal spray coatings, deflectors and scoops are the most common and numerous. One caution before jumping headlong into thermal spray as a solution is for clear glass products. Flecks of the coating may appear in the final product. But if that isn’t a concern and you want to lengthen your time between swabbing, reduce friction, and wear, thermal spray coatings may be the solution you’ve been looking for.
Thermal spray coatings have many benefits. From wear and corrosion resistance to dimensional restoration, it can fit into many manufacturing and maintenance initiatives. Unfortunately, there are some environments where thermal spray coatings are not a good fit. Along with part geometry and coating thickness, there are environmental limits such as abrasion, loading, and service temperature for thermal spray coatings.
There are many different types of wear that a part can experience. Thermal spray coatings aren’t a fit for all of them. Thermal spray coatings are mechanically bonded. This means they are held onto the part by the internal stresses and the frictional stresses between the coating particles and the surface. This works great in sliding, rotating, and galling wear. On the other hand, in some environments, like impact or point loading, the coating could crack and chip off. For example, ones where rocks would hit the coating surface, especially on an edge. Another example of environmental limitations is bending or tension loading.
One thing that contributes to the wear resistance of thermal spray coatings is their hardness. But this also means that they are not as ductile. Any bending load or flexion will inevitably crack the coating. In the same vein, anything that pulls on the coating could potentially pop the coating off. Depending on the type of thermal spray process used, the coatings can handle anywhere from 1,000 to over 10,000 psi pull strength. Flame and Arc spray processes fall on the low end of this range while plasma, HVOF, and HVAF will land on the higher end depending on the coating material. Not only should you look out for incompatible loading scenarios, but the service temperature of the part can also limit whether a thermal spray coating is a good fit.
While not often, we do run into this limitation in specialized situations. When we say, service temperature, we mean the temperatures and temperature cycling the parts will see when in operation. This limitation will also vary by coating composition. On the lower end are your metallic alloys; they can typically withstand up to 500-800 °F. Some specialized ceramic materials can be used at temperatures up to 2000 °F. There are some non-ceramic coatings, such as Hastelloy C-276, that can safely operate up to 1800 °F. There are less common thermal spray materials that can withstand higher, but they are not readily available materials and are usually much more expensive than standard thermal spray coatings.
After these temperatures, you begin losing wear and corrosion resistance reliability, as well as risking total coating failure. Another less common concern is thermocycling. If a part sees large spikes in temperature in a very short amount of time, it could cause the coating to fail and come off. This rarely happens but is something to be aware of when considering a thermal spray coating.
An example would be welding on a coating after it has been applied. Adding high heat near the coating or heat that causes the substrate to shrink will cause the coating to come off. We typically recommend leaving at least 0.5” space between any thermal spray coating and a weld that will be done after coating. On a related note, all heat treating should also be done prior to thermal spray coating, except in cases of spray and fuse, or a coating failure will occur.
While these environments aren’t always thermal spray friendly, plenty of environments are. The limiting factors of thermal spray all come down to the bonding mechanism. These environments require a metallurgical bond and would be great candidates for other coating processes such as spray and fuse or hardface welding.
People often assume that the thicker the coating, the better the performance; but this isn’t always the case. Thermal spray has its limitations; from geometrical limitations to coating thickness to the operating environment. Metallic alloys, cermets, and ceramic coatings have different limits for coating thickness. To better understand the thickness limitations of thermal spray we’ll look at why they exist, what variables contribute to them, and what they are.
Cermets: (n) materials that are comprised of metallic alloys and ceramic materials. i.e., tungsten carbide cobalt chrome or tungsten carbide nickel
Thermal spray coatings have thickness limitations because of the way the coatings are applied. All thermal spray processes involve heating up a coating material and propelling it to the part via a gas of some kind, forming splats of coating. These splats build up on the surface of the substrate, creating internal stresses between particles, which form the thermal spray coating. This unique way of coating can create very strong mechanical bonds but due to the internal stresses can only be built up so much. The amount it can build up depends largely on the coating material and the thermal spray process.
The coating material is the primary factor in determining the coating thickness limit. In general, the harder the coating is the greater the limitation. The ductility of the coating is determined by the atomic structure of the elements that make up the material as well as the internal stresses between splats during coating application. There’s more science there on the modulus of elasticity and metals versus ceramics but we’ll save that for another time. Essentially metal alloys are more ductile and can therefore be applied at greater thickness. On the other end of the spectrum are ceramics which are very hard but brittle at greater thickness. Somewhere in between we find cermets, like tungsten carbide, which combine metallic alloys with ceramics to create a more ductile yet hard coating.
Another element of thickness limits is the thermal spray process. Each process uses different methods to heat up the coating material and propel the particles to the part. These factors cause differing limitations among the processes. Some processes, like HVAF thermal spray, are specially engineered to heat the coating particles in such a way as to increase the ductility of the coating. This means that even though HVOF and HVAF are similar processes that typically apply similar materials, HVAF coatings can be built up thicker than HVOF. Coating thickness limits can sometimes be altered by adjusting the spray parameters, but only so much. These variables, along with the coating material selection, will determine the coating thickness limits.
The thermal spray coating material often dictates which type of thermal spray process you can use. Some materials can be applied with more than one process to produce variations in the coating while others can only be applied with one process. Arc and flame thermal spray coatings are typically metallic alloys so they can be built up thicker without many issues; usually up to around 0.25” depending upon the exact material. This makes them great for dimensional restoration.
Cermets, carbides, and ceramics, usually applied with HVOF or plasma can build up to 0.020” thick. Some metallic alloys can be applied with these processes as well and then their thickness limit is dictated by the spray process. There can be exceptions to this rule depending on the thermal spray process and material. High Velocity Air Fuel thermal spray, or HVAF thermal spray, can sometimes be applied up to 0.050” thick or more. For most materials, coatings do not need to be applied at the full thickness limitation to achieve optimum wear and corrosion resistance.
Depending on your coating needs, coating thickness may limit what material or spray process you can use. Most coatings don’t need to be applied as thick as their limit and offer full performance at a fraction of them. The most common scenario that is impacted by coating thickness is the remanufacture of worn parts. When the damage is too deep then a welded or spray and fused coating may be the better choice. Sometimes the damaged areas can be patch-welded before applying a thermal spray coating if the damage is localized to small areas. This will depend on the base material and economic feasibility. If you are unsure if you will run into coating thickness limitations or if want to know if there is a way around them in your situation the best thing to do is to consult with a knowledgeable thermal spray provider who can suggest the right coating or other solution, if necessary.
Thermal spray coatings are not the end all be all. They aren’t the perfect, miraculous solution for all manufacturing wear and corrosion problems. This is probably not something you would expect a thermal spray company to say, let alone write an entire blog series about, but stick with me. In the late 1900’s thermal spray increased in popularity and people attempted to use it in scenarios without understanding the limitations. This scared some manufacturers away from thermal spray for good. It is in the best interest of everyone to learn, not only the benefits of thermal spray, but also, it’s limitations.
The first three we typically check when discussing thermal spray as a possible solution are the geometrical limitations, the coating thickness requirements, and the service environment of the part. To be as clear as possible we’ve split these topics into a series of blog posts on each of the three. The most inflexible limitation is usually part geometry. We’ll start there by exploring why the limitations exist, sharp edge and corner limitations, and inside diameter and line of sight limitations.
Before we get into the limitations of thermal spray, it is important to understand the mechanisms behind them. Most of the limitations, overall, are due to the nature of the bond that holds the coating material to the substrate. Thermal spray coatings are applied using heat and carrier gases to propel coating particles at high velocities onto the substrate. These splats form together to make the coating. This results in a mechanical bond. This type of bond makes certain loading scenarios off limits for thermal spray coatings. In addition, since the coating splats are propelled in this manner, there must be a clear line-of-sight for the coating to be applied properly. This method and the mechanical bond are behind most of the limitations of thermal spray but we’ll start with the ones concerning part geometry.
Since the coating bond is mechanical, if the coating is hit on an edge or a corner that has been coated, it will very likely crack or pop off. Gear teeth, for example, are not good candidates for a thermal spray coating since they, not only experience point loading, but also usually involve coating around a corner.
Corners become an issue due to the exposed edges of the coating. Even for cylindrical rolls it is generally preferred to have machining shoulders on either side of the coating to help protect the edge of the coating from chipping. Another common term for the shoulder that protects the coating is called a dam. If you can design the coating length and location this way, it can be blended into the shoulders during final grinding eliminating any contact with the edge of the coating in the operating environment.
The exception to this would be spray and fuse coatings. Although applied in a similar way to thermal spray coatings, they are fused afterwards by heating up the coating. This creates a metallurgical bond. These coatings often do better if they can go around an edge and often adhere better this way. Sharp edge and corner limitations can make thermal spray difficult on irregularly shaped parts. While not limited to, it works best for round, cylindrical parts and flat areas with no corner or edge loading. Another difficult geometry is inside diameter locations.
Thermal spray is a line-of-sight process. Line-of-sight describes the direction the coating particles will flow from the spray gun. There must be a line-of-sight from the end of the gun to the coating location. Different thermal spray providers will have different limitations depending upon their thermal spray equipment. This affects many types of part geometry but is most prevalent for inside diameter, or I.D., coating locations.
In contrast, chrome plating is applied via a dip process. This type of coating can flow into small diameters and onto irregularly shaped areas. For a thermal spray coating to be applied to an inside diameter, with a traditional gun set up, the diameter of the bore must be greater than the desired depth of the coating.
There are inside diameter guns, or I.D. spray guns, that can go down into bores, etc. but they are only available for certain thermal spray processes and are different depending upon the thermal spray provider. The smallest feasible diameter is typically around 4” to 5” in diameter with the ability to go as deep as 24 to 48”. This mostly concerns inside diameter and bore coatings, but also apply to a part that requires coating on multiple faces. Since it is line-of-sight, the part must be positioned differently for very faces you coat. This can increase the price of thermal spray coating beyond feasibility.
These geometrical limitations are just the first checks when evaluating the feasibility of thermal spray as a coating solution. There are other exclusions that involve coating thickness capabilities and loading and operating environment tolerance. There are also exceptions to these geometrical limitations that specialized tooling can be used to overcome. The best way to determine feasibility is to work with a trusted thermal spray provider to evaluate specific parts and use cases.
The food and beverage industry is a staple of our everyday lives. If this industry isn’t producing well, we won’t eat or eating costs a whole lot more. Keeping these manufacturing lines running and running efficiently is one key aspect of keeping the cost of essential food items manageable. All manufacturing equipment wears out eventually but in the high volume and speed environments of food manufacturing lines, there are some parts that wear out faster and cause significant maintenance down time. This in turn causes lost production time and increases the overall cost of the product. One way to mitigate these costs is to prevent the wear and corrosion issues in manufacturing components before they start. This lengthens the time between maintenance shutdowns and prevents unexpected ones. One of the easiest ways to do this is through hardfacing.
Hardfacing is a broad term used to describe adding hard material to a less hard substrate. This can be anything from thermal spray, to welding to laser cladding. The benefits of each of these types are numerous and each one has its own place in the world of enhancing the life of food and beverage manufacturing equipment. Let’s explore three scenarios in which hardfacing could help extend the life of components: screw conveyors, conveyance rolls, and packaging equipment.
Screw conveyors and augers are used to move a variety of media in food production. Some of which are very abrasive. The best hardfacing for these are either welded or spray and fused. These provide metallurgically bonded coatings that can extend the life of these components. They can be used to protect the flights of the augers or even the roots if the environment requires it. There are many different materials that can be used depending on the temperature, pH, and other factors of the operating environment.
On a smaller scale, hardfacing methods in the thermal spray family can be helpful for conveyance rolls. Not just for wear but for maintaining performance on production lines. Like the print industry, the tension in production lines is important for maintaining automation and timing. Thermal spray coatings can increase friction and prevent wear to, not only create longer times between maintenance, but better production efficiencies. Different thermal spray coatings and methods of application can produce varying surfaces of roughness to fit the need of the situation.
Another important factor in food production is packaging. Packaging equipment, like any other manufacturing equipment, experience wear from repeated motion and use. Thermal spray coatings can be used to protect these surfaces and extend their service life. Parts like slitters, fingers, and guides can all benefit from wear and corrosion resistant thermal spray coatings. Even better, these coatings can be removed and reapplied to ensure that parts last even longer.
Hardface coatings such as thermal spray coatings as well as hardface weld coatings can add great value to the food and beverage industry. Screw conveyors, conveyance rolls, and packaging equipment are just a few examples of the applications of these coatings. Wherever there is excessive wear or corrosion, hardfacing could be the solution. It is not the end all be all, but it can fit well in the food and beverage industry. If you have manufacturing equipment that is wearing out every few weeks or months, a protective coating may help keep it running at optimum performance longer. A hardfacing supplier should be able to help you determine if their coatings are the right fit.
The benefits of hardface welding or spray and fuse coatings are many and amazing. They are impact and abrasion resistant and can stand up to some of the toughest wear environments. As with any industrial wear solution, there are benefits and things to consider when deciding if it’s the solution for you. Due to the heat involved in creating these coatings there are three things you will want to weigh when considering a hardface weld or spray & fuse coating; base material compatibility, when and how to do the final machining, and how to prep the coated area for application.
Base materials will react differently to the heating cycles of welded coatings as well as spray and fuse coatings. These coatings are hardened materials; so, if the base metal moves too much while coating it can result in hairline cracks in the coating or even failure due to cracking. For example, Nitronic 50 and 17-4 PH stainless steels are not recommended for spray and fuse coatings because the coating will usually crack and can even come off when fusing. These parts can sometimes be processed but if you have an option to use 300 series stainless steel or Inconel 625, etc. your costs will be lower, and the process will be easier. Once you have the right base material, you need to know how to machine it prior to coating.
No matter what material you choose, the base material will move during hardfacing or applying spray and fuse coatings. This means all final machining on areas other than the coating area should be left oversized. When heat is applied, everything will suck in. Inside diameters will go smaller, lengths will get smaller. The part needs to be designed beforehand to account for this. For example, if applying the coating to the outside diameter of a sleeve, the inside diameter will get smaller and the length will shorten. Everything will “move in.” To ensure enough material is present you will want to leave stock on these dimensions. This also affects any holes or threading on the parts. You must wait until all coating is done to machine these details into your part. The one area you don’t want to leave extra material is the coating location.
Welded coatings, especially, tend to be thicker than other coatings such as thermal spray coatings. If your part has tight tolerances, you must account for the coating thickness. Most of the time the section to be coated should be undercut to the depth of the desired finish thickness of the coating. This dimension will also move but is mitigated by the addition of the welded material. The weld will be built up past the final dimension and machined to the proper dimension after coating.
Hardface weld and spray and fuse coatings are very great solutions when they are incorporated into the initial design of the part. Since they cause dimensional changes, they often can’t be added on as an afterthought to a part the way that thermal spray coatings can be. You must be careful to select the best base material and design the part dimensions to account for coating thickness and dimensional changes due to heat. A company that applies hardface coatings and spray and fuse coatings should be able to suggest dimensions or base materials that would be compatible with the coatings you are interested in to aid in the design of the part.
Hardfacing is a broad term used to describe any metalworking process that applies a harder material to a substrate to provide protection of some kind. Most commonly for wear and abrasion, hardfacing can also offer protection from corrosion or impact damage. There are many hardfacing methods such as thermal spray, laser cladding, and welding. For aggressive wear scenarios, people typically look towards a hardface weld coating due to its metallurgical bond. The two most common material families applied this way are Stellites and Colmonoys. To take a better look at these two material families, we’ll talk about the most common types, the differences between them, and the best applications for each.
Stellite® materials are cobalt-based materials while Colmonoy® materials are nickel-based. Nickel-based and cobalt-based coatings are named as such for the material that makes up most of their composition. They are both families of alloys that contain differing amounts of other elements such as carbon, chromium, boron, silicon, iron, molybdenum, and some containing tungsten carbide as well. Most alloys in each family can be applied via thermal spray, welding, or spray and fuse. Examples of nickel-based coatings are Colmonoy® 88 and Colmonoy 6. Some popular alloys of cobalt-based coatings are Stellite® 1, Stellite® 6, Stellite® 12, and Wallex® 50. These variations in alloy composition are the reasons behind the differences between these two material families.
The foundational difference between the cobalt- and nickel-based coating families is hardness. As is typical with most hardfacing solutions, increasing hardness means decreasing ductility. But just because a coating is harder doesn’t mean it’s the right one for every wear situation. Nickel-based coatings tend to be harder which handles abrasive wear better but may crack in impact wear situations. Cobalt-based on the other hand are more ductile and handle impact wear a little better, especially when welded. With cobalt-based you do have to be careful at higher temperatures because their hardness will decrease as the operating temperature increases. Due to their more ductile nature, cobalt-based coatings do handle metal-to-metal wear better and tend to have a lower coefficient of friction. The cobalt-based coatings may also handle corrosion better in certain situations. Neither material family is superior to the other but can be best matched to certain operating environments.
Due to its ductile wear properties and metal-to-metal performance, cobalt-based coatings do well as valve steam coatings, bushing coatings, piston rod coatings, and many more. Some will still prefer nickel-based coatings for these situations instead due to their superior performance at high temperatures. In hard abrasive environments like material handling screw conveyors, nickel-based coatings will offer the most protection. Other applications for nickel-based hardface coatings include valve seats, ball valves, and other valve components. Both material families have countless other applications in various industries.
As with most coating solutions, each material has its best use case. Nickel-based and cobalt-based coatings are no different. Welded and spray & fused nickel-based and cobalt-based coatings offer high wear protection in harsh, abrasive environments. Their variations are slight so working with a professional coating manufacturer is advised. They will be able to assess your operating environment and recommend which of these materials will be best.
Welding, in some form, has been around as far back as the Middle Ages; joining metal for fabrication and structural purposes. These are very valuable applications for welding but not the only ones. We are quite fond of one form that is often overlooked, hardface welding. Hardface welding is the application of specialized alloys onto the surface of a part to create a superior surface. This primarily uses welding processes such as TIG, MIG, or PTA welding. Hardface welding creates many benefits for parts in harsh operating environments, including abrasion resistance, impact resistance, and corrosion resistance.
Abrasive wear is a type of mechanical wear that results from one surface rubbing against another. In our industry we sometimes use this term a little differently. We say abrasive wear is when the contact surface of the substance causing the wear is more harsh and more concentrated as opposed to two surfaces rubbing up against each other. For instance, sand or sharp cutting edges against a surface. Hardface weld coatings excel in environments that involve this point type contact and harsh abrasion due to the way it bonds to the substrate. This is the same reason they are also impact damage resistant.
While other hardfacing methods, such as thermal spray, can often be harder (up to 70 HRC) they are merely mechanically bonded to the substrate. A mechanical bond relies on frictional forces to adhere the coating to the surface of the part. This puts them at risk for cracking or chipping in point load or impact wear situations. Since coatings applied via hardface welding are metallurgically bonded, meaning they form a homogeneous bond where the two surfaces meet, they can handle impact wear and point load situations, like aggregate or cutting teeth. This metallurgical bond also aids in the corrosion resistant properties of hardface welding.
Hardface weld coatings, because they are metallurgically bonded as opposed to mechanically bonded like thermal spray, are able to handle harsh chemical environments. In addition, the most common hardface weld materials, nickel-based or cobalt-based, offer corrosion resistance in and of themselves. These materials as hardfaced weld coatings are not just wear and corrosion resistant at standard temperatures, they are also resistant at high operating temperatures; up to 1500 °F. Between abrasion, impact, and corrosion resistance these coatings are phenomenal when it comes to protecting components in harsh operating environments.
What makes hardface welding and its coatings the most beneficial is an environment that needs all three of these benefits. Due to the cost of the materials in these alloys and the nature of the process to apply them, they are often a premium cost coating. Despite the up-front cost of coating, when used in the right scenarios, they can save you thousands, if not millions, of dollars in the long run. With these hardface weld coatings, parts will run at optimal condition for longer, lengthening maintenance cycles and reducing downtime. Not only will reducing downtime save you time and money, but it can enable you to fabricate parts from more economical alloys like carbon steel and apply the harder, welded coatings to the areas that need it. An in-depth knowledge of metallurgical properties must be used to assess whether your situation warrants hardface welding or if another solution would be a better fit.
Metallizing is a term that has been used throughout the years to encompass many forms of metal coating. It is defined as any process that applies a metal coating to another metallic or non-metallic surface. Someone, depending on the industry and who you’re talking to, could be referring to many different industrial processes, including thermal spray. They could also be referring to hot-dip galvanizing, cold spray technology, and many more.
In our experience, when people ask us about metallizing, they are usually looking for twin wire arc spray or flame spray. Processes that lay down economical layers of basic metals and alloys. Some common metallizing materials with these processes are stainless steel, aluminum bronze, zinc aluminum, brass, and many more. You will even see some metallizing for proprietary alloys such as Hastelloy© or Wallex©. Let’s look at our three most common metallizing materials.
Stainless steel metallizing is our most popular form of metallizing, most commonly 300 series and 400 series. 400 series stainless steel can be used for dimensional restoration up to about 0.20 inches thick. It lays down fast and with minimal raw materials needed making it a very economical way of remanufacturing surfaces. 300 series stainless steel coatings can only go to about 0.020” thick reliably but are also considered food grade which makes them a great solution for the food and beverage industry. Stainless steel metallizing also offers mild corrosion resistance over tool steels and other more common base materials.
Metallized aluminum bronze is typically used for bearing sections, sliding wear scenarios, and to help reduce friction. It has roughly twice the strength and hardness of other bronzes making it a great wear resistant coating that can be easily machined. In addition to wear, due to the porous nature of the thermal spray used for this metallizing, it also readily accepts and stores lubricants in the coating helping to reduce friction. This is great for bearing sections since it is hard enough to increase service life but soft enough to conform to bearing sections as they deform. It can also offer mild corrosion resistance, especially compared to other arc sprayed bronzes, but if corrosion is the culprit, you may want to explore metallized zinc aluminum.
Zinc Aluminum metallizing is used as a sacrificial corrosion coating. It is applied over the base material to “take” the corrosion and protect the underlying surface. Another popular sacrificial corrosion coating is TSA coating or thermal spray aluminum metallizing. The addition of zinc to the aluminum aids in preventing under rusting and increases the time it takes the corrosion to eat through the coating. Zinc aluminum coatings have performed very well in salt fog tests, sometimes lasting up to 20 plus years.
There are many different types of coatings that could be considered metallizing, and each form is a valuable tool for heavy industrial companies. Whether that is one of these thermal spray options or another type of metallizing. It is good to be specific on what problems you are hoping to solve so you can ensure that you have the right type of metallizing for the job.
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Tungsten carbide is used in many different applications from wedding rings to drill bits. As an integral part of the coating world, tungsten carbide coatings help many heavy industrial companies stay up and running longer. Not all tungsten carbide coatings are the same. There are many different chemical compositions of tungsten carbide thermal spray coatings with varying percentages of tungsten carbide and various metals to tailor the coating for different environments.
Tungsten carbide itself is a ceramic and therefore very hard, but brittle. With the addition of metals, like cobalt and nickel, you can increase the ductility of the overall coating and improve its performance. There are countless different formulas and compositions but the ones we apply the most are tungsten carbide cobalt, tungsten carbide nickel, and tungsten carbide cobalt chrome.
Tungsten Carbide Cobalt
Tungsten Carbide Cobalt (88WC 12Co) is a wear coating that helps with sliding wear, abrasion and fretting resistance. As a rule, thermal spray coatings don’t typically handle impact or point loads well, but tungsten carbide cobalt does offer some impact wear resistance. Tungsten carbide cobalt is not very corrosion resistant therefore it is best in dry environments. One great application for this material is feed rolls; whether for paper, sheet metal, or other products.
Tungsten Carbide Nickel
Tungsten Carbide Nickel (90WC 10Ni) is also a wear coating but offers more corrosion resistance at a lower hardness. It also resists sliding wear, abrasion, and fretting. Since this tungsten carbide does not contain cobalt, it will not degrade in a radioactive environment. It works great for ball and gate valves among other applications.
Tungsten Carbide Cobalt Chrome
Tungsten Carbide Cobalt Chrome (86WC 10Co 4Cr) is a wear and corrosion resistant coating often used as a hard chrome plating alternative. It is harder than both tungsten carbide cobalt and tungsten carbide nickel, reaching up to the 70 HRC range, and excels in abrasion wear resistance and erosion fretting resistance. Tungsten carbide cobalt chrome is our most common material of the three and can also be applied with our High Velocity Air Fuel (HVAF) process creating a much more ductile and harder coating with superior corrosion resistance than HVOF applied tungsten carbide cobalt chrome.
Different Tungsten Carbide Coatings, Different Applications
Each of these tungsten carbide coatings will provide wear resistance and extend the service life of your part. The key to the best solution is matching the right chemical composition to the right operating environment. For instance, some will do better than others in wet or corrosive environments. Temperature limitations are also another factor to watch for in coating selection. It is often best to work with a reliable thermal spray company to determine which one is right for you.
Each thermal spray process has a few materials that it is really good at applying. There are also some coating materials that can only be applied by certain processes. One of those coating categories is ceramic thermal spray coatings. Due to the high melting point of ceramics, it requires a very hot thermal spray process to apply them. The only thermal spray process that fits that bill is plasma thermal spray. Plasma spray uses an electrical arc to dissociate and ionize hydrogen and argon gases. This creates a maximum flame temperature of around 12,000-35,500°F. For reference, the next hottest thermal spray process, twin-wire arc spray, only gets up to 7,000°F. The ceramic coating powder is then injected into this stream and applied to the surface of a part. Three common ceramic coatings are chrome oxide, aluminum oxide, and titanium dioxide.
Chrome oxide is our most requested ceramic coating. Chrome oxide coatings come in a variety of chemical formulations that accent various strengths. To keep things brief, we will stick to chrome oxide coatings as a whole. Chrome oxide coatings are generally selected for their wear resistance to chemical exposure. It is wear resistant up to 1000°F in most cases and up to 350-400°F in corrosive chemical environments. It has the highest wear resistance of the ceramic coatings. It is commonly used for sealing surfaces in pumps, textile rolls and food processing equipment.
Chrome oxide coatings have a hardness of 62-70 Rockwell C; depending upon the chemical formulation. They can typically be applied anywhere from 0.003” to 0.025” thick. The best surface finish possible with grinding and polishing is an 8 Ra-in but a better surface finish can oftentimes be achieved with superfinishing. It is the best combination of hardness and smoothness but can be costly compared to other ceramic coatings.
Another beneficial ceramic coating is aluminum oxide or alumina. This coating is most selected for its dielectric and thermal barrier properties. It is wear and heat resistant up to 3000°F. It’s dielectric strength is estimated to be around 300 to 400 volts per 0.001” of thickness at room temperature. It can withstand exposure to the aqueous alkali solutions in some industrial cleaners such as lye, ammonia, and nonphosphate detergents. It is commonly used in motor housings, liners, pump seals and for non-conductive rollers. It also has a low coefficient of friction compared to other ceramic coatings.
Alumina thermal spray coatings have a hardness of 60-66 Rockwell C and can be applied anywhere from 0.005” to 0.020” thick. One limitation of aluminum oxide is surface roughness. It typically can only be finished down to 20 Ra-in which, while good, is higher than other ceramic coatings. Both, chrome oxide and aluminum oxide, can be on the premium side of thermal spray coating materials. If budget is a concern, you may want to consider titanium dioxide.
Titanium dioxide can be easier on the budget and a decent solution in moderate wear environments up to 1000°F. It has good corrosion resistance except in the presence of alkalis and sulfuric acid. It is best in sliding wear situations and for wear from abrasive grains. It has a hardness of 50-53 Rockwell C and can typically be applied anywhere from 0.005” to 0.025” thick. It can achieve a surface roughness down to 8 Ra-in. If you are looking for the smoothness of chrome oxide but not worried as much about hardness, titanium dioxide can be a cost effective alternative to chrome and other ceramic coatings. For this reason, it earns its place in our three most common ceramic coatings.
If you are looking for a coating to resist wear and chemical corrosion with a smooth surface finish, chrome oxide is your best bet. If you want some chemical corrosion and surface roughness benefits without some of the cost and aren’t worried so much about wear, you can try titanium dioxide. If you are after a dielectric coating or a thermal barrier coating, then you can go with an aluminum oxide. Each ceramic coating, including the ones not mentioned here, is valuable for one purpose or another. The best way to choose what is right for you is to look at the problems you are trying to solve with your coating and do lots of research or reach out to a trusted thermal spray company for a recommendation.
Most people we encounter have either been using thermal spray for years or they have never heard of it. The latter is even more common when hiring for thermal spray technicians. Most have never heard of thermal spray, let alone know what a thermal spray technician does. Every thermal spray company is a little different, but let’s talk about some things you can expect a thermal spray technician to do.
Small vs. Large Quantity Thermal Spray
There are essentially two types of thermal spray work: job shop and production. Job shop work typically consists of smaller quantities of one-of-a-kind parts. They usually have something a little unique about them that usually requires some ingenuity and attention to detail. Production work consists of large quantities that are processed at regular, consistent intervals. If you want to learn more about how thermal spray can be used on production parts, check out our other blog. A thermal spray shop is usually a mix of both, to varying degrees.
Production style work usually means you can come in for the day and someone else has set everything up and you can load parts and press go. Most of your day is spent watching your process parameters and checking quality requirements.
For job shop style work, there are multiple different types of parts each day that require more set up and problem solving. This offers a diverse workday for most thermal spray technicians, which includes things like reading work orders and part drawings, setting up tooling and equipment for processing, and troubleshooting coating and equipment issues.
Reading Work Orders and Interpreting Part Drawings for Thermal Spray
The first task in the thermal spray process is reading the work order. The work order outlines the steps that a part will undergo while receiving a thermal spray coating. It also outlines what the incoming part size will be, what the coating material is, and how thick it should be after spray. Information from the work will also tell you the spray parameters for the equipment so that the coating material is applied properly.
A thermal spray tech could also be required to interpret part drawings to figure out coating location and what sections of the part to protect from unnecessary coating. Once it’s clear how to process the part, you will need to begin prepping it for thermal spray.
Prepping a Part for Thermal Spray
To achieve high quality thermal spray coatings, there is quite a bit of prep work to do before you turn on the spray gun and go to town. There is tooling needed to rotate and hold parts in a specific way, robot programming to ensure consistency and efficiency, and most parts require some sort of masking and blasting step.
Masking refers to the use of liquid masking, thermal spray masking tapes, or metal plates to shield certain areas of the part from overspray. Sometimes this is as easy as putting a pre-made plug into a hole; other times there are multiple layers of tape or multiple types of masking for one part. Blasting with aluminum oxide grit is almost always used before the coating is applied to create better adhesion. This is either done robotically or it is done in small blast cabinets prior to putting the part in the spray booth.
For job shop style work, there could be multiple different jobs in a day that each require a different set up and robot program. For larger production jobs, a senior level thermal spray tech will typically set up the job and a different thermal spray technician will have the tasks of loading parts, pressing start, and unloading parts on repeat.
Both production and job shop work require monitoring for equipment issues and quality checks on the parts during and after spray. They also require techs to pay attention to detail and think critically about what is going on throughout the entire thermal spray process.
Thermal Spray Coating Application
During the spray process the thermal spray technician monitors the process to ensure the coating application goes smoothly. Thermal spray technicians are trained to identify when there is an issue with the equipment or when a coating is not going down as it should. Each coating material and thermal spray process has its unique things to look out for.
They may also use temperature monitoring equipment to ensure the part is staying at optimum temperatures. Spray techs will use precision instruments to measure coating thickness between gun passes and after final coating. Thermal spray is a noisy process, so while the spray gun is running it is typically observed from outside of a spray booth while wearing hearing protection and safety glasses.
Anyone Can Learn
A career in thermal spray can be a rewarding and lifelong career. If you enjoy being challenged to apply your critical thinking skills to solve problems or like the idea of seeing how many high-quality parts you can spray in a certain time frame, there is a place for you in a thermal spray shop. There are many opportunities for upward mobility a career in thermal spray. Often, upper-level management in a spray shop is promoted from the shop floor.
Like welding or machining, thermal spray is a trade that is need of good, hardworking people. If you are interested, you can check out our website on the Our Careers page under the About Us section or look up a shop in your area. Either way, the thermal spray community looks forward to hearing from you.
The basic purpose for scientific experimentation and lab testing is to prove or disprove a hypothesis. Lab testing in the thermal spray world uses industry standard testing procedures to prove the quality of a coating. The results can be used to proof the spray parameters, process, and set up of a coating application. When investing in a coating for a long-term, high volume production run of parts, this is typically done in the research and development phase. There are three basic types of lab testing that are beneficial for thermal spray coatings: bond strength, hardness testing, and microstructure analysis.
Bond strength testing examines the adhesion of the coating to the substrate surface. This is done by spraying a metal plug with the desired coating and testing according to ASTM C633. This test uses high strength epoxy to attach a coated plug to a test plug. A tensile machine then pulls the plug apart and measures at what load the coating fails. Most of the time with HVOF or HVAF coatings, the coating bond will be stronger than the epoxy resin bond. This is why the bond strength is typically listed as 10,000 psi.
Most thermal spray material and process combinations have a known range of bond strengths that are possible. Poor bond strength results usually indicate an error or issue in the application process. While bond strength can be an issue to determine coating failure versus function, hardness testing will be an indicator of the wear resistance potential of the coating.
Hardness testing is only one indicator of the potential wear resistance of a coating, but it can be powerful in determining if a coating is applied within specification. Like bond strength, most material and spray process combinations have known hardness ranges. Hardness can be tested using macro or micro-hardness depending on what loads the coating will undergo in the intended operating environment.
A common hardness test used in thermal spray applications is Vickers microhardness testing using Vickers hardness testing. This test uses lighter loads and can be done on a representative sample rather than on the part itself. These are usually small coupons sprayed under the same parameters and processes as the parts. Often hardness testing is done in conjunction with microstructure analysis to get the fullest view of the coating quality.
Microstructure analysis uses a high-powered microscope on a cross-section of a coating to examine porosity and coating structures. A test coupon is sprayed with the coating in question and the sample is cut and mounted in a mold for examination. The photos taken by the microscope are then analyzed to determine porosity and check for: cracking, delamination, oxides, unmelted particles, and/or embedded grit leftover from blasting. All of these could weaken the coating indicating an issue within the coating process.
While you do not need these tests on every coating or part, it is good to know that they exist and how they correlate to coating performance. Testing is valuable when using a coating material or process for the first time. It is especially important if you are planning to use a coating for a long-term, high quantity production run of parts.
These lab tests are often required for industries with an increased safety risk should coating failure occur, such as nuclear power generation or aerospace. If you are wondering if you should do any lab testing for your next thermal spray coating, it’s best to reach out to your coating provider. They may already have recent lab data they can share, or they can advise if testing would be necessary or beneficial.
We talk a lot about the benefits of thermal spray to companies hoping to remanufacture their damaged parts but one of the best applications of thermal spray coating is to apply it to new parts before they experience harsh operating environments. Some parts can even be made complete, meaning machined from stock material and coated, in one facility. This eliminates the increasing logistics and lead time issues that are running rampant in today’s COVID-19 climate. The biggest differences between thermal spray for remanufacture and thermal spray for new production parts are initial service life, engineered wear and performance characteristics, and process efficiency.
While thermal spray coating a part before operation increases the up-front cost, it will also cause the part to last longer before needing repair. If you’re replacing a roll every two weeks because it’s wearing out so much, coating it from the very get go will space out your maintenance cycles and make unexpected downtimes less frequent.
When you add thermal spray coatings up-front you can also tailor the characteristics of the coating, not just in respect to wear. Ceramic coatings can be used to insulate and mitigate heating. Dielectric coatings can help mitigate electrical conductivity issues. Parts in harsh chemical environments can benefit from chemically inert coatings. Sacrificial corrosion coatings can help protect the underlying material for parts in water and marine environments. So not only are there wear benefits to protective coatings but many other coating characteristics that can help make parts last longer.
Planning ahead to thermal spray your parts, means you choose how many and when. With higher part quantities, you can have highly developed coating processes which increase efficiencies, coating quality and cost effectiveness. Dividing set up and programming time between more parts means a lower cost per part. A good thermal spray company will have engineers on staff to help develop these processes and monitor the coating quality.
While thermal spray is a great fit to repair and overhaul a damaged part, there are significant benefits to protecting your parts before they experience the harsh environments of operation. While it may cost you more up front, it can lengthen your maintenance cycle interval and decrease down time for repairs. It can also aid in other areas of production such as temperature mitigation or electrical conductivity. Preventative coatings in high quantities can also lower the cost of coating. So instead of waiting for disaster to strike, evaluate what parts could benefit from preventative coatings before going into service to see if production thermal spray is the right fit for you.
Arc thermal spray, also known as twin wire arc spray, is one of the older and simpler forms of thermal spray coating. Thermal spray technology has come a long way over the years, from spraying basic metals and simple alloys to, now, spraying extremely hard ceramics and carbides. These advances don’t mean that arc thermal spray is any less valuable. We’ll be the first to tell you that thermal spray isn’t the cure all so you can believe us when we say that each process has a specific fit in the coating world. Among many things, twin wire arc thermal spray is great for dimensional restoration, sacrificial corrosion coatings, custom alloy coatings, and bearing surfaces.
Dimensional Restoration
The most basic use of arc thermal spray is dimensional restoration. Rotating parts often experience surface erosion over time from rotating inside sleeves or collars. This creates problems when the parts wear out of round and become unbalanced. Not only is this noisy, but it can also decrease operating efficiencies and the vibration can cause damage to other machine components. Arc spray can be used to remanufacture the surface of the part, up to a quarter of an inch, and restore it to OEM specifications. This is great for many parts including pump shaft repair, print roll repair, or hydraulic cylinder repair; to name a few.
Sacrificial Corrosion Coatings
Another application of arc spray is sacrificial corrosion coatings. Using Aluminum and Zinc-Aluminum, arc spray can provide an anodic layer over steel. This layer can attract corrosion and keep the underlying surface protected. Arc spray coatings are also porous so they can accept sealants more readily than a regular carbon or tool steel surface, so parts stay sealed longer.
Custom Alloy Coatings
One advantage of arc spray that is unique to this thermal spray process is how the spray material is fed during application. The gun used to apply this type of coating feeds two separate wires, charging them negative and positive, and causing them to arc and melt. Compressed air then propels these molten droplets onto the surface of the part. Since it uses two wires, you can create custom alloys by feeding two different material wires. One example is carbon steel and bronze to create a more wear resistant bearing surface coating than plain bronze. You can also combine a 316 stainless steel with a Molybdenum wire to create an economically friendly anti-galling coating. There are many combinations that can be explored and engineered to fit the operating environment of the part.
Bearing Surfaces
The application of thermal spray to bearing surfaces using arc spray allows the use of many materials for softer bearing surfaces. Soft bearing surfaces are used to allow deformation so that the bearing area can accommodate small amounts misalignment. Arc spray can apply bronze, babbitt, brass, and aluminum bronze. Using thermal spray to apply these as coatings, as opposed to making the entire part from these materials, is not only more economical but has the added benefit of porosity. Like sealants, the porous surface more readily accepts lubricants and holds onto them longer. Arc spray bearing surfaces can also be removed and reapplied again and again when they get worn and no longer operate at peak performance.
Affordable Wear and Corrosion Surface Solutions
The purpose of any thermal spray coating is to keep your parts operating at peak performance for longer, whether that’s through preventative coatings or remanufacture. Arc spray offers many unique solutions and is one of the most affordable forms of thermal spray coating. So, whether you are struggling with corrosion or bearing area issues, arc thermal spray could be the solution you’ve been looking for. Contact us to see if arc spray, or one of our other processes, could be the solution you've been looking for.
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Agriculture and farming are essential to the American economy and lifestyle. Billions of people rely on the midwestern states, known as the bread bowl, to provide their everyday sustenance. With fewer and fewer generations continuing in the family business of farming, optimizing farm has become more important than ever. Finding the right technology is paramount in helping farmers and equipment manufacturers create the best harvesting and planting equipment at economical prices. Thermal spray technology is one of those solutions. Thermal spray is a coating process that applies metallized coatings to the surfaces of machine components to enhance their performance and service life. Thermal spray coatings can help prolong the effectiveness of farm equipment by fighting wear and abrasion, protect components from corrosion, and restore damaged parts to OEM specifications.
From ground engaging equipment to threshing elements, thermal spray coatings can help increase the wear resistance of surfaces. Tungsten carbide and chrome carbide coatings can be used to increase the productivity of threshing elements such as rasp bars or concaves by prolonging their effective service life. Ground engaging surfaces can also benefit from wear and abrasion resistant coatings by creating a harder contact surface on cutter bars and header prongs. Spray and fuse technology can create metallurgically bonded coatings to meet the needs of equipment used in highly abrasive environments such as buckets and scraping blades. In addition to wear, many of these coatings are also corrosion resistant.
Corrosion is the ever-present enemy of agricultural equipment. Not only is this machinery exposed day in and day out to the elements, but they regularly encounter harsh chemicals from chemical treatments and fertilizers. Thermal spray can apply a corrosion resistant coating over the top of aluminum and carbon steel components, such as spray booms and plow bottoms, to fight against corrosion and create a barrier. Thermal spray can also apply sacrificial coatings such as zinc or zinc aluminum to keep the corrosion from effecting the underlying surface of the component. Wear and corrosion damage can be prevented with thermal spray but sometimes life just happens.
When parts do fail, whether from wear and corrosion or something else, thermal spray can also be used to build the surface of components back up to OEM specifications. After the damaged sections have been removed, thermal spray can build up the surface with stainless steel or other material and even overlay it with a carbide to prevent future wear damage. All of this can be machined back to down to precise size and surface finish. A thermal spray remanufacture can not only add new life to a part but extend its life by engineering wear and corrosion resistant surfaces.
Overall thermal spray can make agricultural components last longer at peak performance and restore worn or damaged components back to peak performance. Whether through metallurgically bonded spray and fuse coatings or mechanically bonded thermal spray coatings, this technology can protect and enhance components such as spray booms, hydraulics cylinders, augers, and more. Contact us to find out if thermal spray is the solution to your agricultural wear and corrosion problems. We can help you investigate your wear and corrosion problems and discover if thermal spray is the right fit to meet your needs.
There is a myriad of surface coating solutions on the market that solve many different problems. Hard chrome plating and thermal spray are just two, of many, that are available to industrial manufacturers to resist wear and corrosion damage. For years thermal spray has struggled to compete economically with hard chrome plating for certain industrial applications, namely hydraulic cylinders.
Hard chrome plating has cornered this section of the market by being able to apply thin layers of smooth coating that require little to no finishing, saving time and money over the most comparable thermal spray method, High Velocity Oxy-Fuel (HVOF).
The reason HVOF can’t always compete is largely due to spray material. HVOF can’t accomplish the thin coatings since the powder used to create the coatings must have coarse particle sizes to withstand the heat and velocity of the HVOF application process. This means thicker as-sprayed coatings and causes increased grinding time to meet the required dimensions and surface finish of hydraulic cylinders. Thermal spray just couldn’t compete unless the parts were too large for hard chrome tanks or the operating environment was highly corrosive…until recently.
High Velocity Air Fuel, or HVAF, was invented in the late 1990’s to early 2000’s but hasn’t made its way through the market until recently. Using advanced gun technology, HVAF lowers the heat of application allowing for the use of finer cuts of spray material. This gives us the ability to create thin layers of tungsten carbide coating with a lower as-sprayed surface roughness that can be easily finished to OEM dimensions and finishes. This specific type of HVAF coating is known as Flash Carbide.
Flash Carbide, a play on the term Flash Chrome, is a thermal spray coating that is applied quickly with minimal prep and finishing due to advances in the gun technology. These coatings can outperform hard chrome plating in certain situations. The HVAF technology also creates harder yet more well bonded coatings. For more information on how HVAF coatings and Hard Chrome Plating compare on issues like hardness, bond strength and cracking check out the other blog post in our Enhancing Surfaces series.
So while Flash Carbide is not a materials-based, speedy comic book superhero, it is a great solution for hydraulic cylinder remanufacturers, or anyone else, who is experiencing rising chrome prices. There may even be performance benefits that outweigh hard chrome even if the cost was a little more in certain situations. Flash Carbide can keep your rods and cylinders running stronger for longer. But it doesn’t stop there, HVAF technology can be used in many different ways on many different industrial components to prevent wear, corrosion, and even cavitation damage for pumps.
Just like every other surface solution out there, there are going to be areas where one excels over the other. The important thing is to do your research, talk with a trusted coating provider who will be honest about their applications and limitations, and every once in a while, give something else a try to see if it could enhance the life of your components.
Hard Chrome Plating has been around in some form since the early 1800’s. It’s popular in many industrial and automotive applications and has been a great surface coating solution for many years. Unfortunately increasing costs, due to environmental regulations, have many people asking, "Is industrial hard chrome plating still the best enhancement solution?" At HTS Coatings, we talk a lot about our HVAF technology and often tout it as the most comparable thermal spray alternative to hard chrome. But when we put them side by side, how do they match up?
Even we will admit that hard chrome has its place, as with most surface protection technologies. For instance, small inside diameter parts, below 3.5 inches, will be more suitable for hard chrome plating. Sometimes, due to the geometry of the part, hard chrome will be more economical. But with advances in thermal spray technology and the increasing environmental pressure against hexavalent chrome, using HVAF thermal spray technology to apply our BTHC-0005 coating is comparable pricewise and quality-wise with hard chrome plating. So, let’s take a look at how BTHC-0005 stands up against hard chrome in the key performance areas of wear and abrasion resistance, cracking, corrosion and friction.
Wear and Abrasion Resistance
The first thing you might think of when determining wear resistance is hardness. On a basic level, the harder the material, the greater the wear resistance. This is technically correct but can also be misleading. For a great explanation of this, check out this article by Superior Consumables. It’s wise to look at a variety of factors and tests to determine wear resistance.
If you look at the graph below, you will see the hardness in Vickers for our BTHC-0005 coating and for standard hard chrome plating[2]. As you can see, not only does this coating hold its own, but it also offers better hardness.
We can also look at ASTM G65 wear data for BTHC-0005 and Hard Chrome Plating[4]. G65 testing determines abrasion resistance based on how much volume is lost in a controlled load and speed. You can see from the graph that BTHC-0005 has less volume loss than hard chrome plating under the standard testing environment.
When it comes to wear resistance HVAF technology is certainly comparable to hard chrome plating and even outperforms it for certain materials and in certain wear environments. So far HVAF coating is comparable to Hard Chrome, but since it is a mechanical coating bond, let’s see how it measures up when it comes to cracking.
Cracking
Cracking is usually a function of coating ductility and a little bit of bond strength for thermal spray. Ductility can be measured by looking at the young’s modulus of the coating. Not only is this dependent upon the chosen coating material but it can be greatly affected by the coating process itself. The graph of Young’s Modulus, a measure of elasticity, below shows that BTHC-0005 is more ductile than Hard Chrome plating[6].
You can also look at something called Fracture Toughness. Fracture toughness uses something called stress intensity factor. It looks at the critical stress level of a sharp crack where the propagation of the crack suddenly becomes rapid and unlimited. Fracture Toughness for BTHC-0005 and Hard Chrome Plating[8] are roughly the same despite the mechanical bond of the thermal spray coating.
Hard chrome plating has a molecular bond of about 35,000 psi, so it wins out on sheer bond strength. But since HVAF has a greater than 12,000 psi bond strength, it still serves most industrial environments since it is a more ductile coating. Cracking can be an issue for any coating, but corrosion resistance is another key property to look at when comparing HVAF and Hard Chrome plating.
Corrosion Resistance
Corrosion is a natural chemical reaction and can occur when parts are in a harsh industrial environment or even just in normal operating conditions. It’s important to know your parts are protected. Corrosion occurs at different rates in different materials but when it comes to coatings, porosity is key. It can be difficult to quantify porosity in hard chrome plating since it is naturally cracked during coating formation. During a salt spray corrosion test, BTHC-0005 passes the 1000-hour test. Hard chrome plating can pass about the 150-hour test[10], as seen below.
Hard chrome plating can offer some corrosion resistance but if corrosion is your main worry, HVAF will be best. Another reason you might choose Hard Chrome is the surface finish capabilities and how they might affect friction in your system. Let’s see how BTHC-0005 and Hard Chrome compare when it comes to friction.
Friction
Friction is another key area that hard chrome plating excels at and, until HVAF, cornered the market on. Before, thermal spray required a lot of grinding and polishing to compete with hard chrome which drove the price beyond what was economical. Now, many HVAF coatings, including BTHC-0005, have an as-sprayed roughness of around 32 Ra, are sprayed thinner and can be easily polished, without grinding, to 0 Ra. This saves time and money and brings the price of finishing into a competitive range with even Flash Chrome.
The Right Solution for You
If you’ve been using hard chrome and it’s been working for you, great, but if you’re feeling the pressure of rising prices or just want to try something different, it may be time to consider other options. Thermal spray, specifically BTHC-0005, can be a cost-effective, comparable solution. Hard chrome will always have its place when it comes to surface solutions and so will thermal spray. Knowing what you need from your surface coatings is the key to determining which of these processes will be best to enhance the life of your machine parts. For more information on thermal spray processes and applications, check out our thermal spray page.
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In recent years the internet has greatly changed the buying process, certainly in the business to consumer market but also in the business-to-business market. You may not even realize that your buying habits have changed. With the answers to most of your questions just an internet search away, businesses are relying more on internet research to identify their problems and determine the ideal solutions rather than on the friendly, neighborhood salesperson.
According to CSO Insights, “70% of buyers fully define their needs on their own before engaging with a sales representative, and 44% identify specific solutions before reaching out to a seller.” While this ability is great, you may miss out on some key first impressions of a vendor. Being able to ask the right questions once you do speak to someone has become more important than ever.
After you’ve done your research and know that thermal spray is the solution you want to look into, what kind of questions should you be asking to determine which vendor is the right one for you? We’ve compiled five questions we think are key in helping you determine which companies will provide the quality thermal spray solution you should expect. From standard procedures to EPA disposal, how should a thermal spray company conduct themselves to earn your business?
You are trusting this company with your equipment. You should get to know what will happen to it. Also, if a company has a written set of procedures that means they’ve sat down and thought about the best way to do things, which typically means your part will be better cared for. If a company knows what they’re doing they should have these at the ready for potential customer review and shouldn’t fear a quality audit or even a shop visit. If you sense tension on the line when you ask these questions, take heed. You should also ensure their standard procedures include steps for quality and coating checks.
Sometimes you won’t have to ask this question if you are already aware that they are ISO 9001 certified, but it still wouldn’t hurt to know if they have the capabilities to perform lab testing. You can ask how these companies measure the quality of their services. Do they use micrometers or thickness gages, such as an Elcometer, to check coating thickness at regular intervals along the part and throughout the spray process? Do they have a coordinate-measuring machine, or CMM, to measure spherical or complicated surfaces such as valve balls? These tools and procedures will ensure that your part will return to you at your desired dimensional specifications.
Coating quality is another topic to ask about; do they measure their coating quality using industry standard lab tests? Do they outsource their lab testing or do they have an in-house lab for faster result turnaround? The most common coating lab tests are bond strength, hardness, porosity and basic coating structure. If you need certain coating properties, such as friction mitigation or anti-slip coatings, you will want to ask about surface roughness testing as well.
While you may not need these tests every time you have a part sprayed, it is good to know whether a company has a plan in place to evaluate their processes and coatings and if they have those services available to you, should you desire them. It is also important to know whether they keep up with regular calibration of their lab and thermal spray equipment; as well as their measuring devices. You can even ask to them to provide certifications of calibration for their equipment, if you desire.
After asking about lab testing, it’s a good idea to ensure the quality of the lab tests and equipment. The results you request will mean nothing if the vendor is not doing regular machine maintenance and monitoring. This also applies to all of their service equipment and measuring devices.
This starts in their prep processes such grinding or machining. Do they regularly check their grinding wheels to ensure the grit effectiveness? Do they have a preventative maintenance plan in place to mitigate errors from machine breakdowns?
This gets even more crucial when it comes to thermal spray equipment. Have their powder feeder pressures been checked? Do they regularly check their gun pressures and temperatures? Do they obtain material certifications for their wires and powders? These things will not only affect the quality of your part’s coating but also affect their process times and materials, potentially costing you extra time and money. An easy way to ensure consistent, quality thermal spray coating is the use of robotic technology.
Robotically controlled thermal spray is the most consistent way to apply coatings. Asking if they spray via programmable robots or similar mechanical devices, such as bug tracks, is a good indicator of the quality of coating you will receive. Mechanically controlled thermal spray guns apply more even coatings and allow for exact control over spray parameters which highly affect the hardness and bond strength of the coating. Some parts and processes will require hand spray and can’t be fully automated, but knowing a company uses robotically controlled spray guns will show you how seriously they take their spray parameters and coating quality. Another thing a thermal spray vendor should take seriously is what they do with the byproducts of their processes.
Some of the materials used in thermal spray operations such as chrome carbide powder and aluminum oxide grit are considered hazardous substances and require special steps for handling, storage, and disposal. While this may not have a direct impact on the quality of your coating, it says a lot about the character of the people you’re working with. Proper material handling displays a sense of responsibility for the work they are doing. If they aren’t taking care to dispose of their materials properly, they might not be taking the utmost care for your parts either. If you sense forethought and care in the way they answer this and other questions, you are on the right track to finding the thermal spray company for you.
In the business-to-business market there’s a lot of competition out there and it can be hard to weed out who to trust with your machine components. While a cheaper price might be tempting, you may be sacrificing on quality. Not getting the answers you want on one of the above questions might not be a deal breaker but working with a company who is able to answer these questions with poise and planning, says a lot of about the quality of work you will receive.
In the world of surface coating, there are many options available to extend the life of parts and most of them are very similar in one way or another. While thermal spray has been around for a long time, cold spray is relatively new on the scene having been developed sometime in the 1980’s and 90’s. While cold spray is technically a subset of thermal spray, its application does not require a combustion process like most thermal spray applications. Cold spray and thermal spray differ in three main ways; process parameters, coating materials and the resulting coating properties.
The first thing you notice is the term cold versus thermal. It paints a clear picture of the most distinguishing way these processes differ. Cold spray relies on kinetic energy via high velocities to deform the material particles and adhere them to the surface of the part. This means that while the process gas is heated anywhere from 90 to 2,000° F, the particle temperature usually remains below 400° F. The gases in cold spray are heated, not to warm up the powder particles, but instead to increase the velocity of the gas and therefore the material particles. This is also aided by the use of a nozzle inside the spray gun to achieve supersonic velocities. Other thermal spray processes, such as HVAF Spray and Plasma Spray can range from 3,500° to 35,500 ° F. HVAF and HVOF can also reach supersonic velocities using similar nozzle technology.
These processes both propel material through a spray gun but rely on different raw material forms to do so. Thermal spray uses many different process feedstocks depending on which process you are using. Arc spray uses electricity, where the more premium process, HVAF, uses hydrogen, nitrogen and propane. Cold spray relies on nitrogen or helium gas, or sometimes just air, to create the velocity needed to deform the material particles and apply it to a substrate.
Cold spray coatings are applied by either a low pressure or a high pressure spray system. High pressure operates at around 300-1000 psi while low pressure operates below 300 psi. They also differ in that low pressure injects the powder material after the nozzle throat while high pressure injects it prior to the nozzle throat. High pressure is used for applying high strength metals and alloys and low pressure is used for spraying softer metals and mixtures of metals and ceramic powders.
Both Cold Spray and Thermal Spray apply similar coating materials. The big difference is the particle size of the powder that can be sprayed. Cold spray can spray much finer particles, including nanocrystalline powders. Cold spray powders typically have a grain size of 1-50 µm whereas thermal spray powders vary from 10-100 µm depending on the specific thermal spray process. Some thermal spray processes, such as Flame and Arc, can spray materials in wire form.
While cold spray can spray many materials, it has yet to be reliable in spraying economically available tungsten carbide or ceramics. These cold spray applications are yet to be fully developed but some nanocrystalline combinations are available. Cold spray excels with more ductile materials such as bronze, stainless steel, zinc, and aluminum. Technology is still being developed to spray harder more brittle materials which tend to rely on high heat for thermal spray coating.
Cold spray and thermal spray coatings have mostly the same properties since these are heavily dependent upon the feedstock material being applied. Where cold spray excels is material oxidation. Oxidation is a chemical interaction that can occur during spraying where the metallic particles oxidize over their surface. Since cold spray utilizes plastic deformation of the material particles via high velocities as opposed to melting with heat, the particles are in a solid state when they contact the part and therefore experience no oxidation. With thermal spray a small amount of oxidation does occur over the particle surface.
Figure 2 - The nature of thermal spray coatings. Source [1]
While oxidation can be detrimental to corrosion, strength, and machinability; it can also increase the hardness and wear resistance of a coating. Oxidation can be mitigated in thermal spray processes by controlling process parameters such as standoff distance, reducing flame parameters, using an inert environment, or using compressed air cooling.
Although material choice largely dictates coating properties, these processes do differ in the residual stress they create in the coating after spraying. Cold spray results in compressive residual stress whereas thermal spray has tensile residual stress. While cold sprays bonding mechanism is not thoroughly researched, at least from readily available sources, it is believed to be largely mechanical interlocking and some metallurgical bonding between particle interfaces. This metallurgical bond between particles combined with the compressive residual stress means, in general, less potential for coating cracks. As with most coating properties in thermal spray, potential cracking can be mitigated with properly engineered spray parameters.
Cold spray is an emerging coating technology engineered for low spray temperature applications. It is well suited for the aviation industry and some specialty applications since it allows for minimal part distortion. It is a great low heat solution. While both it and thermal spray offer similar coating materials, thermal spray may be a more economical solution in some circumstances and is offered by a wider variety of providers. As with any thermal spray coating, cold spray included, material and spray process selection come down to your priorities.
If you have a part that is prone to distortion but need a premium corrosion solution, then cold spray is a coating solution worth looking into. If you’re more concerned with coating hardness and wear resistance, then some other thermal spray options, such as HVOF and HVAF may be better options. Being a relatively new technology, cold spray has its limitations, as does any thermal spray process. It will be interesting to see where this newer technology leads the thermal spray industry in the future.
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A lot can happen in five years and a lot has happened at HTS Coatings. Five years ago, this month, HTS Coatings opened its doors as HB Coatings. Not only did our name change but many other things as well. We sat down with Jason and Ashley Hunsaker and asked them to reflect on what these first few years have been like…
For HTS Coatings, establishing our mission and vision changed the entire culture out in the shop and throughout the entire company. In order to carry out this mission and vision, Jason and Ashley also established our four core values: Willingness to change, high expectations, gratitude and camaraderie. Let’s hear from Jason and Ashley their heart behind each of these values…
We like to sum up our vision in one, two-word phrase, “Enhancing Life.” We desire to not only enhance the life of machine parts, but also enhance the lives of those we come into contact with. Whether that be our HTS family, our customers or our vendors. Listen to these stories of how God has been enhancing lives at HTS Coatings…
God has been good to HTS Coatings these last five years and we have many hopes for the future. We are most excited though to see how God continues to write our story.
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While you won’t find "hardfacing" in the dictionary, it’s an industry standard word that anyone looking to repair and remanufacture their machine parts would benefit to know. Hardfacing is any metalworking process where harder or tougher material is applied to a base metal i.e. a machine part surface. This describes anything from thermal spray to laser cladding to weld overlaying. All of these use various heat sources to apply metallized coatings.
In a previous post we compared laser cladding to thermal spray and briefly described the difference between a mechanical and metallurgically bonded coating. In most industrial scenarios, a mechanical bond will suffice but what about when it doesn’t? Laser cladding isn’t your only metallurgically bonded option, outside of spray and fuse thermal spray. So, let’s take a look at how laser cladding compares to the different hardface weld overlay process on the market today.
Each process is performed differently, with laser cladding being the most different in application. Laser cladding is the use of electrically produced laser light to heat wire or powder material and apply it to a substrate surface. Each of the weld overlay types are relatively similar with small but significant differences between them. MIG (Metal Inert Gas) welding, or GMAW (Gas Metal Arc Welding), uses electricity, a shielding gas and a consumable electrode. This consumable electrode is typically the material used to overlay the substrate. TIG (Tungsten Inert Gas) welding, also referred to as GTAW (Gas Tungsten Arc Welding), uses the same raw materials except that, instead of a consumable electrode, it uses a nonconsumable tungsten electrode and an additional rod of the overlay material.
A more recent type of welding process, PTA (Plasma Transfer Arc) Welding, is the similar to TIG welding in raw materials but instead of a rod filler material, it uses a powder material and a specialized nozzle to ionize the shielding gas and create a plasma arc to apply the material to substrate surface. When it comes to overlaying capabilities, PTA is the most comparable to laser cladding; but that does not discount the other two.
Each of these processes produces an overlay that is metallurgically bonded to the substrate. This means that the overlay material and the substrate material fuse together at a molecular level. This has many advantages including the decreased surface porosity that results in high performance, corrosion resistant coatings. Laser cladding and weld overlays also result in extremely wear resistant coatings.
Each of the weld overlays range in thickness from approximately 0.05 inches to about 0.1 inches. Laser cladding has a slightly wider range at 0.008 inches to 0.15 inches thick.
The most black and white difference between the four process is the materials it can overlay. MIG welding is the most limited, only applying steels and stainless steels, nickel, flux cored wire and hardface wires. TIG welding, along with PTA welding and laser cladding, can apply the popular overlay metal, Stellite® 6 and other cobalt based alloys, as well as the nickel and tungsten carbide-based alloys of the Colmonoy® alloys, including Colmonoy® 88. TIG welding can also apply 316 stainless steel, carbon steel and other wire metals. PTA welding and Laser cladding can also apply other stainless steels such as 300 and 400 series stainless steels.
A huge advantage of Laser Cladding is something called Heat Affected Zone, or HAZ. HAZ is the zone of the substrate metal that has not melted but, has been subjected to the elevated temperatures of the process for a brief period of time. This alters the molecular structure of the metal in this area and it no longer possesses the desirable properties of the substrate material, but since it has not melted, it hasn’t assumed the properties of the solidified, overlay. This HAZ is a weakened layer that affects the hardness and porosity of the underlying microstructure.
Typically weld processes with a higher heat input have a larger heat affected zone. Laser cladding, since it requires the lowest heat input of each of these processes, has the smallest HAZ. Despite having the highest heat input, PTA has the next best HAZ. This is due to the faster cooling and quenching of the overlay material. It does, however, still have the highest heat input of the weld processes, so heat distortion can still be a concern since it is performed at approximately 50,000°F.
Each process has specific benefits and limitations in respect to deposition rate, positioning and the control of process variables. Laser cladding is typically a robotically controlled process which provides unparalleled consistency but also limits it in deposition rate and positioning. PTA welding is the fastest overall with a skilled operator. TIG weld overlay, while slower than PTA weld overlay, is faster than MIG weld overlay and can be done in most positions, although overhead welding can be difficult and requires highly skilled operators. MIG weld overlay cannot be done on vertical or overhead surfaces. These variables can of course be eliminated by careful planning and tooling when applying harface weld overlays.
TIG welding provides good temperature control while PTA welding and laser cladding provide excellent control over their process parameters. MIG welding can be difficult to maintain consistent temperature and arc, requiring skilled craftsmen to create a quality overlay.
So, while each process has its pros and cons, they all produce high quality, corrosion and wear resistant coatings. All of the weld overlays; MIG, TIG and PTA, can produce coatings similar to laser cladding with PTA being the closest by far. Laser cladding and weld overlays vary greatly in heat input and the resulting coatings vary slightly in thickness capabilities and materials. Laser cladding excels when heat distortion is an issue for smaller parts or parts made of heat sensitive metals. In situations where temperature isn’t an issue and laser cladding might be overkill, weld overlays provide an economical, hardfacing solution.
For more information about PTA Welding, check out our other blog post: Plasma Transfer Arc Welding for Abrasion Resistant Coating or check out the welding services that HTS Coatings offers.
We live in the information age; you can find the answer to almost any question in minutes. Doing a simple internet search for “machine part repair” or “remanufacture” will result in thousands of ways and processes to rebuild your parts and get them working again. The hard part is figuring out which advice to take and who to trust. The even harder part comes when there are multiple kinds of repair processes that seem, at first glance, to do the same job. If you have ever wondered what the difference is between laser cladding and thermal spray and which one is right for you, then you’ve landed in the right spot.
In the broad scheme of things, laser cladding and thermal spray accomplish the same goal. They can be used to add a hardened, new surface to previously damaged or worn industrial components. They can perform remanufacture and even prevent future wear.
Most people look to laser cladding due to its metallurgical bond but there are thermal spray processes that can achieve this as well. So, which one should you choose? Let’s break it down and look at each one individually.
Laser cladding is a hardfacing process that uses laser energy to melt and weld powder material to a surface. The result is similar to hardface welding but operates at a much lower temperature; around 1000°F as opposed to 11,000°F for TIG welding. It forms a metallurgical bond with the substrate material and produces a hard, wear resistant coating.
The biggest advantage to laser cladding is the metallurgical bond achieved at relatively low temperatures. Since laser cladding uses metallurgical bonding, there is little to no porosity in the coatings, resulting in fantastic long-term corrosion resistance.
Laser cladding also allows for thicker build up on a single pass compared to other processes. Overlapping passes meld together to produce a quality surface. This combined with low metal dilution, means there is minimal post-process machining.
Laser cladding is a mostly robotically controlled process. While this creates greater precision, it also less versatile. Not only is the system not portable, it can create complication for larger parts.
Laser cladding typically only applies a few materials. Nickel and cobalt-based alloys such as Inconel®, Hastelloy® and Stellite®. Some stainless steels, such as 300 and 400 series, and carbides, such as tungsten carbide. These are great for wear and corrosion resistance but can fall short if you require other coating properties.
Like most advantages, thick build up, also has its downside. Since laser cladding lays down so much in one pass, it can struggle when thin coatings are required. High build rate can also lead to cracking.
Thermal Spray encompasses a wide variety of processes. Most use a gas or electricity to create a flame in order to melt the wire or powder materials and apply them to a substrate. Some, such as spray and fuse, produce metallurgical bonding; while most others use mechanical bonding.
Thermal spray can be used to apply a variety of materials, including the materials used in laser cladding. Additional material options can be used to supplement the coating properties. In addition to wear and corrosion resistance, thermal spray coatings can be used to create dielectric, thermal barrier and electrically conductive coatings. One thermal spray process, Arc Spray, can feed two different materials to produce an engineered alloy coating.
Thermal spray processes can lay down coatings as thin as 0.002”, thinner in some cases. The ability to spray in thin layers can also aid in producing coatings in situations when precise coating thicknesses are required. Thermal spray can also build up thicker coatings by doing multiple, robotically controlled passes.
Due to its versatility, thermal spray can also be sprayed in the field. Unlike laser cladding, thermal spray guns can be operated independently of robotics and can produce quality coatings with skilled operators. The typical robotically controlled thermal spray set up can also handle intricate geometries without thick build up in corners and on edges.
Thermal spray can require more masking to protect against overspray compared to the focused spray area of laser cladding. Since most thermal spray processes use mechanical bonding, machining and grit blasting are usually required before coating application which can lengthen the process.
Spray and fuse thermal spray can accomplish metallurgical bond but at a higher heat than laser cladding, around 1,900°F to 2,050°F. High Velocity Air Fuel, or HVAF Spray, is lowest in temperature at around 3,500°F and is mechanically bonded.
Depending on the process you use, there is low to high porosity for thermal spray coatings. This can be a long-term issue with certain coating materials in highly corrosive environments if not sprayed correctly. Porosity helps minimize coating stress and reduces cracking but also interferes with surface finish, strength and microhardness. Oxides are introduced during the thermal spray process, which can increase hardness and wear resistance, but can also cause corrosion, strength and machinability issues.
Both thermal spray and laser cladding can produce wear and corrosion resistant coatings. There are advantages and disadvantages to both. The best way to choose is to decide what exactly it is you’re looking for in a surface repair or coating. If you need a metallurgical bond and temperature is an issue, then laser cladding is the way to go. If you need a thin coating of material, then you should look to thermal spray. If you need your coating to do something other than just wear and corrosion resistance, you should look at the different coating materials possible with thermal spray. Depending on your situation, either one may work, and you might be better off getting a quote for each process and seeing how they compare in cost for your specific part.
Long have we considered what we do a noble addition to the manufacturing industry. One that helps our customers reduce waste and keep their parts in production longer. It wasn’t until recently that we realized that we were contributing to something larger than ourselves; that others in the industry were having this conversation.
The conversation about stewarding the resources we have by considering ways to make things last longer and reuse the resources already in production. This idea has come with many names over the ages; recycling, going green and now the most wide-reaching approach, circular economy.
Circular economy is a systematic approach to economic development designed to benefit business, society, and the environment.[1] It is best understood by contrasting it with a historically prevalent economic model: linear economy. In a linear economy, we take resources, make a product and throw it out. In contrast, a circular economy seeks to find opportunities to keep materials and products in use.
Circular economy, according to the Ellen MacArthur Foundation, has three principles:
This principle seeks to take an intentional look at manufacturing processes and decide if there are ways that one can reduce waste or use more sustainable methods and materials.
This means to seek to extend the life of the things you are already using or to find a way to restore things and continue using them.
A circular economy avoids using non-renewable resources. You can do this by choosing renewable materials or finding a way to use a byproduct of your manufacturing in some way.
These principles outline what it means to embrace a circular economy, but why is it important to the manufacturing industry?
We have known for a while that our resources are not endless. There is only so much ore in the world to be mined or trees that can be harvested without causing short- and long-term environmental effects. Implementing the principles of a circular economy ensures that we make the most of the resources we are already using and protecting our ecosystems from overuse.
Along with environmental stewardship, we also face an economic responsibility. By taking this seriously now, we can mitigate the risk of resource depletion as well as prevent unstable commodity prices. Often times, adapting circular economy principles causes the creation of new jobs and new business opportunities which aid in the overall success of our economy. If small changes we make now, can ensure a better economic future, why not invest in these principles?
Although change can be scary, there’s no denying that reusing something or making it last longer will save money. If we can do something economically responsible and temper environmental concerns, all while saving ourselves money, why wouldn’t we? Not only do circular principles provide cost savings during the manufacturing process, it also provides cost savings on raw materials and consumer goods by driving market prices down. All while keeping waste out of landfills. With all the benefits to the manufacturing industry, how do we go about implementing these principles?
In order to achieve a circular economy in manufacturing specifically, we have to begin looking at value retention processes, or VRP’s. Value retention processes are methods that retain value in the system by adding value and utility to a product and/or extending the useful life of a product beyond its expected end-of-use.
This includes practices such as choosing repair and overhaul over buying new or purchasing remanufactured equipment as opposed to new. A great example of circular economy would be instead of buying a new pump, buying a pump with remanufactured components. There are many avenues to accomplish these things, but one answer has become abundantly clear for us…thermal spray.
Thermal spray can be used in any of the above mentioned VRP examples. Thermal spray repair can reduce waste by repairing damaged machine parts. Thermal spray coatings can keep machine parts in use longer by increasing wear and corrosion resistance. Thermal spray can also be done over and over allowing you to reuse the same machine parts again and again.
We have had customers report that parts they once switched out every two days, now last over four years. Even as we look at our own manufacturing processes, there are many ways we can use thermal spray to repair parts within our own shop.
"...it would have to be changed every two days (keep in mind we are a 24/7 operation), now we haven’t changed one out for wear since we started with the coating, probably 4 to 5 years." -Valued Customer
So maybe we’re late to the game on terminology but we believe in the processes we perform. We have always known the value of using thermal spray to extend the life of machine parts and aid our customers in economic, efficient manufacturing solutions. Whether that has been through repair or surface enhancement. If we are to take our long-term stewardship of our environment and our economy seriously, we have to begin to implement these value retention processes and contribute to a circular economy.
Friction. The resistance that one surface or object encounters when moving over another. We live everyday experiencing varying degrees and scenarios of friction. The scrape of pushing a chair back to stand up, the scratch of sandpaper on wood, the wear of a print roll shaft as it rotates. All examples of friction, some desirable, some not. In most industrial situations we seek to reduce friction, but in some select scenarios friction isn’t only okay but essential.
The most ideal example that comes to mind is for the printing and packaging industry. Most feeding operations require something to be fed through many rollers in a uniform manner to ensure precise placement. These rolls, such as pacing rolls and pull rolls, benefit from friction. In printing for example, better surface tension means faster press speed. Better friction prevents web slippage and ensures tight starts. All of these could result in an increase in production. When more friction is beneficial, thermal spray coating can be a cost-effective way to increase surface roughness.
Since friction is involved, a good thermal spray friction coating will also be a wear resistant coating. Carbides like tungsten or chrome carbide, ceramics, stainless steels and nickel alloys such as nickel chrome are great candidates for anti-slip coatings. When deciding between these coatings you can look at factors such as the desired roughness, budget and coating hardness to determine the best solution.
While in-feed rolls are our most common high friction coating, these coatings have many applications. Parts such as reel drums, winders, carpet rolls, traction rollers, friction discs, and grip fingers are all good candidates for thermal spray friction enhancement. Friction increasing coatings can also be beneficial on tool surfaces, part holders, tooling fixtures and collets. Thermal spray can also be used for safety coatings such as grates, sidewalks and stair treads. For the packaging industry, some converting and cutting parts can benefit from friction coating as well.
While many ways exist to increase friction on surfaces, thermal spray can be an efficient, budget-friendly industrial solution that also extends the service life of parts. Especially in the printing and packaging industry, thermal spray coatings can increase efficiency and prevent web slippage. Since many materials can be used to create thermal spray high friction coatings, they come with other benefits including wear resistance, corrosion resistance and even dielectric and thermal barrier benefits if desired.
Many industrial components are good candidates for these coatings. Thermal spray can even be used to build up previously worn surfaces while easily adding friction characteristics to salvage used parts. If the coating wears down and loses its efficiency, it can easily be stripped and recoated without the expense of a new component, while keeping the old parts from the scrap bin. This form of remanufacturing is a large benefit of thermal spray and can aid in promoting a circular economy. Overall thermal spray is a beneficial solution to increase the friction of industrial machine parts.
The United States is the largest remanufacturer in the world. From 2009-2011 remanufacturing supported 180,000 full time jobs and was a $43 billion industry in the U.S.[1] The remanufacturing industry can pertain to anything from office furniture to heavy-duty equipment and is the key to a healthy, circular economy.
Remanufacture has many benefits and is a key component in reducing waste. It can also reduce lead times compared to ordering new parts. A lot of times remanufactured components can also be purchased at a lower price than new. Despite its many benefits, remanufacture can be easily misunderstood and even more difficult to distinguish from other repair-type processes.
Depending on where you look, you will get many definitions of the word. According to Merriam-Webster it is, “the rebuilding of a product to specifications of the original manufactured product using a combination of reused, repaired, and new parts.”
If you ask the Remanufacturing Industries Council, “Remanufacturing is a comprehensive and rigorous industrial process by which a previously sold, worn, or non-functional product or component is returned to a ‘like-new’ or ‘better-than-new’ condition and warranted in performance level and quality.”
Most definitions you’ll find amount to returning a component to a previous state of functionality. But doesn’t repair do that as well? If we take a look at other words that might be used interchangeably with remanufacture, things start to get a bit confusing.
Both of the definitions above contained some variation of words or phrases like, “repair” or “returned to.” A lot of people use these types of terms interchangeably, and understandably so. Most often we use the word repair but, depending on the industry or environment, many other words can be used to describe bringing something back to working conditions. Take these dictionary definitions for example:
It is easy to see how these terms overlap. So, is remanufacture any different than repair and overhaul? It may be hard to decipher at first, but it is, and the key distinguishing factor is the resulting service life of the part.
When a part reaches the end of its use, you have two options. You can throw it out and buy a new one or you can try to get the existing one working again. To repair a part, you would identify the key issue causing its failure then repair that issue. If you chose to have someone remanufacture your part, that part would go through various, maybe multiple, processes and would end up indistinguishable from a newly purchased part. Each one gets the part in working order again but remanufacture practically starts the life cycle of the part all over from the beginning.
Think of it this way, say a part gives you “x” amount of working service life. When the part breaks down, simply repairing it may only give you “0.5x” in additional service life. Remanufacturing the entire part, by one or more of the methods mentioned above, would give you an additional “x” or more amount of life. Essentially, repair may only bring a part back to where it can function again for a little bit longer whereas remanufacture will bring it back to a “like-new” condition.
To give a real-life example, say you have a print roll with some large divots and wear on the shaft. If you just did a weld repair and patched the divot it would probably function a little longer but soon breakdown again. But if you chose to remanufacture that roll by replacing the entire shaft surface with a new one; maybe you even enhance the surface with a thermal spray coating of wear-resistant material, you could extend the life of your part even further. You probably would still have to use a weld repair to fill in deeper divots before applying the new surface, but you would have a better-than-new part, machined to original equipment manufacturer specifications.
The important thing to remember when searching for a repair solution is that a remanufacture may involve a repair but a repair is not always a remanufacture.
For us, remanufacture and repair are synonymous because all of our repair processes result in a “like new” part. But that may not be true of every solution out there. Be clear when contacting a machine shop or repair shop and ask questions about their processes and quality standards. Don’t be afraid to ask what types of processes they intend to use and the benefits they offer.
Remanufacture encompasses a lot of things. Often times people think of car parts when it comes to remanufacture, but many industrial components can be remanufactured such as; print rolls, pumps and pump components, packaging and conveyance parts, hydraulic cylinders and much more.
Sometimes a simple repair may be all you need to get by. But when you need more or want to extend the life of your parts, look to remanufacture to get the most for your money. You can either purchase remanufactured parts or find someone who will remanufacture the part you already own. Either way, ask the right questions and consider remanufacture the next time your machines or parts break down.
Learn more about our processes or contact us for more information.
]]>I grew up in rural Missouri and can remember sanding wood in my required junior high shop class. It was always by hand and you had all these different grits to choose from. The smaller the number, the more abrasive it was and as a junior high student it was hard to keep it all straight. The same could be said of grinding wheels. Not only are there different grit sizes but there are also different abrasive grain types. So which wheel is best in which situation?
There are many different types of grinding wheels out there for all kinds of different purposes. At HTS Coatings we typically use three types of grinding wheels; aluminum oxide, silicon carbide and diamond. We get into some pretty tough materials and sometimes have to remove a lot of material. We also work with a variety of materials so knowing when to use each kind of grinding wheel makes a huge difference.
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In the 2000 film Erin Brockovich, Julia Roberts plays the title character legal clerk turned environmental activist. The events depicted in the movie are based upon the environmental concerns in Hinkley, California. The investigation looked into the contamination of groundwater supplies with chromium-6, more commonly known as hexavalent chrome. A local power company had been using chromium-6 in some of their compressors to reduce corrosion. This chromium-6 contaminated water would then be discharged into unlined pools. This water then leaked into the local groundwater supply. Hexavalent chrome is recognized by the EPA as a hazardous air pollutant, a priority pollutant under the clean water act and a hazardous constituent under the resource conservation and recovery act. This same compound is the one used in industrial hard chrome plating.
Chrome plating has been around, in various forms, since the early 1900’s and has been used to increase the wear resistance of industrial components for almost just as long. Its long history lends to it being a well-researched and well implemented process. It can easily coat inner diameters and intricate geometries with a high wear-resistant material. Hard chrome plating can achieve a hardness of 700 to 1,000 Vickers. Not only is chrome plating hard, it is also thin. Hard chrome plating is typically deposited from 0.001 inches to 0.004 inches thick, making it good for components in tight tolerance environments. Hard chrome plating also reduces friction, achieving a surface finish of approximately 1 Ra. At a glance, hard chrome plating seems to be the perfect industrial coating solution for hydraulic rods, crane and lift cylinders and hydraulic pump components; but it has limitations.
The process of hard chrome plating is rather complicated and lengthy. Components must be completely submerged plating liquids and transferred to various large tanks depending upon the size of the part. This creates size limitations and high turnaround times. These large tanks are easily contaminated, and those plating imperfections could severely impact performance in the field. Since the whole part must be submerged, it also means that masking areas that should not receive plating is very difficult. This is process is also limited in the materials it can apply and the thicknesses it can achieve.
The process of hard chrome plating is performed by electroplating. Electroplating uses electrical conductivity to apply plating to the surface of a component. This limits the material that hard chrome plating can be applied to. A component must be made of steel, stainless steel, brass, bronze or copper. This will fit most machine components but will fall short on specialized or ferrous materials.
The elephant in the room is the environmental concerns surrounding the disposal of the materials used in chrome plating. During the chrome plating process, chromium is dissolved into the electrolyte solution and becomes very hard to safely dispose of afterwards. If chromium reaches the local groundwater supply, it can cause illness and some even believe it to be a carcinogen. Hard chrome plating has many advantages; but at what cost?
If the cost is too great, is there an alternative? In recent years, thermal spray technology has advanced leaps and bounds and readily competes with hard chrome plating. Thermal spray uses combustion to heat up metallic materials and apply specialized coatings to industrial surfaces. It is like spray painting with metal. Thermal spray has the same wear resistance as hard chrome plating while achieving more corrosion resistance.
Due to its nature of application, thermal spray can be customized using various materials to produce precise coating characteristics. Thermal spray can be applied to the same component materials as hard chrome plating but also some that chrome cannot. Common hard chrome alternatives include tungsten carbide and chrome carbide. While chrome carbide also contains chromium, it is in solid form and in smaller amounts. It is easily contained and disposed of in an environmentally conscious manner. Specialty materials such as Chrome Carbide Hastelloy and Tungsten Carbide Chrome Carbide Nickel can also be used depending upon the corrosion, wear and operating temperatures you may be trying to mitigate.
Thermal spray can be applied down to thicknesses of 0.0015 inch and up to thicknesses of 0.060 of an inch. This can be advantageous when compared to the thicknesses you can achieve with hard chrome. Thermal spray coatings can be built up during spray to exceed the desired dimensions and then machined down to meet tight tolerances. You can also layer coatings for larger build up or for different properties of the coating system. The machinability of thermal spray coatings also lends itself to a variety of polishing capabilities.
Thermal spray coatings can be applied at various surface finishes. High velocity air fuel spray, for instance, has an as sprayed roughness of 40 Ra at a thickness of 0.002 inches. This same coating can be finished down to less than 1 Ra by grinding and polishing. These coating characteristics are the same as those of hard chrome plating but with the added corrosion and impact resistance benefits of thermal spray.
Thermal spray can achieve similar coating characteristics in respect to hard chrome plating but with a smaller environmental footprint. In addition to being environmentally conscious, thermal spray is also inherently corrosion resistant whereas hard chrome plating is only corrosion resistant with additional steps and treatments. The ease of the thermal spray process lends to faster turnaround times and less contamination issues compared to hard chrome plating. Thermal spray can also be portable; meaning it can be brought on location for parts that are too large to transport.
If we take a look back at the Hinkley water contamination, could thermal spray have been the solution to keep corrosion from damaging the cooling water sections of their compressors? While thermal spray will never fully replace hard chrome plating in some instances; it is a valuable alternative for hydraulic rod enhancement, pump component enhancement, and much, much more. For more information, read about our hydraulic cylinder repair or contact us today to see if thermal spray is the solution for you.
]]>Corrosion costs the manufacturing and production industry approximately 17.6 million dollars a year. We see it everywhere; on kitchen knives or the wheel well on a truck. Corrosion is a big issue. Corrosion occurs when metals react with natural elements in the environment to form oxides, hydroxides or sulfides. The most common corrosion cause found in manufacturing components is iron oxide. Ceramics and polymers can also experience corrosion but that rarely occurs before other forms of degradation take place. If we want to keep machine components running longer and prevent corrosion, there are four ways it can be fought.
The most basic way to prevent corrosion is to ensure that components are made of corrosion resistant materials. These materials are typically, formulated metal alloys such as nickel aluminum or 310 stainless steel. The downside to this method is that manufacturing a component solely out of these materials is expensive and it is often hard to justify the cost due to the limited service life of the part. Also, these materials are typically unable to be hardened to a high enough hardness to avoid wear; meaning you sacrifice wear capabilities for corrosion protection. The part will have a good life versus corrosion but could easily fail from the everyday wear and tear of the production environment.
As previously mentioned, corrosion occurs with exposure to the natural elements; usually water and air. To prevent corrosion, ensure machine components are away from unnecessary water sources and protected in a climate-controlled environment. This can be very difficult in the manufacturing industry since most components are used in harsh industrial environments. Most industrial settings involve exposure to water or other corrosive chemicals and materials. Down-hole tooling, for example, may not always come in direct contact with water per say but it will encounter drilling sludge and soil, both of which contain water and other corrosive materials. The same goes for pump components. This solution cannot always be implemented in every working environment.
Beyond protecting it totally from harsh industrial environments, keeping components clean is another way to prevent corrosion. Removing the external materials causing corrosion can delay the chemical reactions that cause corrosion. Keeping components clean requires regular maintenance schedules and time out of production. Have multiple components stored on-hand so a component can be rotated out of service for cleaning, helps with downtime but it can be expensive to keep spares just sitting on the shelf. It is always a good idea to keep your components clean, dry and stored in a climate-controlled environment, but it is not always possible.
We cannot always keep components out of corrosive environments or take the time to clean them after every use. The best solution would be to purchase components made from corrosion-resistant materials, but that is not always financially possible, nor does it offer all of the performance needs there may be. A more economical solution would be thermal spray. Thermal spray can overlay budget-friendly components with corrosion-resistant materials. By adding a protective layer to machine components, it can prevent corrosion and even delay wear and erosion damage. Even if a component has already shown signs of corrosion, thermal spray can be used to repair the surface or stop the damage from continuing. Machining and grinding techniques can be used to remove the damaged material and replace it with a corrosion-resistant surface. Thermal spray is used as a protective coating on new components or as a repair and overhaul solution to previously corroded ones.
The best course of action for preventing corrosion in industrial and manufacturing components, no matter what, is to plan ahead. When purchasing equipment, try and purchase components made of high-end, corrosion-resistant materials. Use components in climate-controlled environments away from the elements, if possible, and clean them regularly. For most, the best solution will be to choose sustainable, budget-friendly thermal spray methods and materials to protect valuable components from corrosion. Whatever way you choose to protect your components, planning ahead is the best bet. To find out more about thermal spray and our services, contact HTS Coatings today!