What is HVOF Thermal Spray and Why Is It Important

Common Types of HVOF Thermal Spray Coatings

1. Carbides (Tungsten Carbide Cobalt, Tungsten Carbide Nickel Chromium, Chromium Carbide Nickel Chromium)

Carbides are the hardest and most wear-resistant HVOF thermal spray coatings. They are often used in mining, construction, oil and gas, turbine engine, and pump applications. All of these coatings consist of carbide grains (tungsten carbide, chromium carbide, or a blend of both) suspended in a metallic binder (usually cobalt or nickel chromium). These coatings are extremely hard wearing, and can provide protection even at very low thickness.

2. Nickel and Cobalt Superalloys

Coatings of Stellite and Tribaloy cobalt alloys and similar materials are designed to withstand repeated metal on metal contact, even under high load and high temperature, without galling or adhering. Coatings in this class are often used on the mating components of turbine engines, which operate at high temperature and often with substantial vibration. The coatings ensure that mating metal components continue to move freely against one another without wearing.

Where Is HVOF Thermal Spray Used?

HVOF thermal spray coatings are widely used in various industries for their excellent wear and corrosion resistance properties. Some of the common applications of HVOF coatings include:

1. Automotive Industry

HVOF coatings are used on various automotive parts such as exhaust valves, cylinder bores, and piston rings. They help to improve the performance of engines by reducing friction and wear.

2. Aerospace Industry

HVOF coatings are used on aircraft turbine blades to protect them from particle erosion encountered during operation.

3. Oil and Gas Industry

HVOF coatings are used on valves and other components in the oil and gas industry to protect them from erosion and wear.

4. Medical Industry

HVOF coatings are used on medical implants such as hip joints and knee replacements. They enhance the surface of these components to promote bone growth.

Why is HVOF Thermal Spray Important?

HVOF coatings are denser than other thermal spray coatings. An HVOF gun creates a gas stream with a velocity higher than the speed of sound, much like a fighter jet engine, but of course much smaller. This super fast gas jet accelerates coatings particles to very high speeds so that they impact the substrate with tremendous force. This high velocity and high impact force causes the deposited material to compress and densify, reducing or removing the pores and gaps that would otherwise form using other thermal spray methods.

The high density and tight bonding of HVOF coatings has two primary advantages:

1. The coating has fewer, if any, pathways to allow corrosive fluids to penetrate the coating and attack the substrate. For this reason, HVOF coatings are less corrosion-prone than plasma or flame spray coatings.
2. The dense structure ensures that HVOF coatings are better adhered to the substrate. All thermal spray coatings are mechanically bonded, and the tighter packing of HVOF particles means that more of the coating material’s surface area is in intimate contact with the substrate. Bond strengths of HVOF coatings are often several thousand PSI higher than comparable plasma applied coatings. 

Conclusion

The HVOF process can provide many benefits for components. These benefits include improved wear resistance, corrosion resistance, appearance, and performance.

If you are looking for coatings for steel parts in the USA, then you can get them from us at Hayden Corporation. We offer thermal spray coating, as well as hardface welding and machining. Get in touch with us for more information.