Thermal Spray FAQ's

What is thermal spray?

Thermal spray, often called metallizing, is a process that uses high heat and carrier gases to melt powdered or wire material and apply it to a surface. It’s kind of like spray painting with molten metal.

What is thermal spray used for?

Thermal spray has many uses but is best known for wear and corrosion resistant coating. It can also be used to remanufacture or repair damaged machine components, for dielectric coating on parts, hardchrome alternative and as a thermal barrier just to name a few other uses.

What are the benefits of thermal spray?

The benefits of thermal spray include wear resistance, corrosion resistance, cavitation damage protection and economical repair solutions. Depending upon the material used in coating, there may be other benefits such as electrical conductivity or thermal barrier. It can also be used in the manufacture of new parts using cheaper non-heat treated base materials and applying coatings for the wear surface.

What is TSA (thermal spray aluminum) coating?

TSA stands for Thermal Spray Aluminum but has come to be used for any sacrificial corrosion resistant coating. Most commonly using aluminum, but some can mean it to be aluminum, zinc or a combination of the two. It is usually applied using arc thermal spray or flame thermal spray.

What are the common applications of HVAF thermal spray?

Most commonly HVAF coatings are applied to machine parts to increase surface hardness. HVAF thermal spray is great for cavitation damage resistance due to its highly ductile nature and good bond strength. It is also great for high wear parts, parts that experience environmental or chemical corrosion and for parts that require a smooth surface or need to meet tight tolerances.

What is the difference between HVAF and HVOF?

The main difference between the HVAF and HVOF process itself is the combustion gas that is used. HVOF uses an oxy-fuel mixture whereas HVAF uses compressed air and propane. HVAF has superior coating performance over HVOF; mainly in the areas of ductility, bond strength and hardness. HVAF thermal spray coatings can be sprayed at thinner coating thicknesses, down to 0.001”, have a smooth as-sprayed roughness, sometimes as low as 40 Ra, and can be polished down to less than 1 Ra more easily.

What is hardfacing?

Depending on who you talk to, hardfacing has many definitions. Essentially it is the addition of a harder material to the surface of another material. To some it is only classified as hardfacing if the deposition of hard alloys is completed through a welding process. Whereas some classify it as hardfacing if any metalworking process is used.

What are the different types of thermal spray coatings?

Thermal spray coatings can be categorized in many different ways such as coating characteristics, coating process and coating material. Thermal spray coatings by characteristic are as follows:

• Wear Resistant Coatings
• Corrosion Resistant Coatings
• Cavitation Damage Prevention
• Thermal Barrier Coatings
• Electrical Coatings (Conductive and Non-conductive)

Thermal spray coatings can also be classified by coatings process:

• Flame Spray (wire or powder)
• Twin Arc Spray
• Plasma Spray
• High Velocity Oxy-Fuel (HVOF) Spray
• High Velocity Air Fuel (HVAF) Spray
• Spray and Fuse

Thermal spray coatings can be classified by the type of material sprayed. A list of our most common coatings materials can be found here.

What materials can be used in thermal spray?

Many metal or ceramic materials can be used in thermal spray. Our more common materials are tungsten carbide, stainless steel and chrome carbide. Check out our Coating Materials page for a full list of materials we commonly spray.

What advantages does thermal spray have over hardchrome plating?

Hardchrome plating is the application of hexavalent chrome to a substrate. Thermal spray is a comparable process that can apply a wide variety of materials, including chrome carbide. Thermal spray coatings are more environmentally friendly, in application and bi-product disposal. Thermal spray coatings can be applied in a wider range of thicknesses over hardchrome especially on thicker buildups. Extremely fine finishes can be achieved on coatings just like chrome especially when using HVAF thermal spray.

Why doesn’t thermal spray coating just flake off?

Thermal spray coatings are applied at temperatures sufficient enough to melt the material and apply it to a component. Most components are prepped using blasting and this, coupled with other spray parameters, creates a mechanical bond between the coating and the substrate. Bond strengths for some thermal spray processes have been measured at over 12,000 psi. Flaking of a coating is typically caused by applying the coating incorrectly or not applying the correct coating for the application.

Does thermal spray coating require a sealer?

Depending on the operating environment of a component, a sealer may be desired. We find this to be very rare and most of our customers do not seal their coatings.

Is thermal spray coating metallurgically bonded to the surface?

Most thermal spray processes are mechanically bonded. If a fusing step is added, i.e. spray and fuse, a metallurgical bond can be achieved.

At what temperature is thermal spray applied?

Thermal spray processes have varying application temperatures. Most are in the range of 3,560 °F to 7,000 °F; the exception being plasma thermal spray which ranges from 12,000 °F to 35,500 °F.

What kind of results do thermal spray coatings have for G65 wear testing?

G65 tests are more dependent upon the material type, not so much on the process.

While some materials we spray offer ASTM G65 Testing data, not all do. Tungsten Carbide coatings typically have a volume loss of 5.5 to 7 mm3 where a Stellite® 6 weld overlay has a volume loss of around 55 mm3.

What thicknesses are thermal spray coatings?

Coating thickness depends heavily upon the thermal spray process used to apply it and the material being applied. Thickness can range from 0.002” to 0.25” thick. In the graphic below you can see how each of the different coating processes compare to one another. This list is a general list. If you have specific questions please let us know and we will be happy to answer them. For more details visit each of our process pages on our Thermal Spray Processes page.

Are thermal spray coatings conductive?

Some thermal spray coatings are conductive depending upon the coating material. Common electrical coating materials are copper, silver, aluminum, molybdenum and alloys of these and other materials. For more information on electrical coatings, read more here.

What about dielectric coatings or non-conductive coatings?

Thermal spray coatings can also be dielectric, meaning non-conductive depending upon the coating material. Common dielectric coatings are usually in the ceramic coating family and include alumina (aluminum oxide), zirconia (aluminum oxide), chromium oxide, titania (titanium oxide) or yttria stabilized zirconia.

Can thermal spray be used in remanufacturing?

Yes, thermal spray is a great way to resurface and repair industrial components. For more information check out our blog on Remanufacture vs. Repair.

More questions?

Contact us, we will gladly answer any questions you have!