The Benefits of Hardface Welding and Its Coatings
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 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.
Impact Damage Resistance
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.
When to Use Hardface Weld Coatings
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.
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