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HVOF stands for High Velocity Oxygen Fuel and is classed as a Thermal Spray Process. All HVOF coatings are characteristically hard and dense in structure with a low porosity and incredibly high bond strength, and the process an be used to spray a number of materials onto a component. This includes carbide and oxide materials.
A huge range of components benefit from thermal spraying, either as part of the original manufacturing process or as part of reclamation and repair. Some materials are used for small niche applications and other materials are sprayed by the tonne. What they all have in common is that component life is significantly prolonged through use of HVOF Coating.
The first stage in the process is to take powdered materials and formulate them into the correct ratios for the coating application. Common materials include; Tungsten Carbide, Nickel Alloys, Ceramics, Stellite 6, Chromium Oxide and more. We are also able to combine different materials in order for us to provide a bespoke solution to your application.
HVOF coatings go by a wide variety of brand names, which can often cause confusion. WOKA, Amdry, Diamalloy and Metco are just a few examples. If you have a Spec you are unfamiliar with, please ask us if we are able to provide this. In many cases the base materials are the same as we would already use, just under a different brand name.
Components will most often be Shot Blasted before coated. With the Coating Composition selected, it is fed into our Thermal Spray gun where it is essentially heated up and fired out. HVOF utilises confined combustion and an extended nozzle to heat and accelerate the powdered coating material. Typical HVOF devices operate at hypersonic gas velocities, i.e. greater than MACH 3. The extreme velocities provide kinetic energy which help produce coatings that are very dense and very well adhered in the as-sprayed condition.
In order to properly control this process, the coating is applied using a state of the art KUKA robotic arm to ensure repeatability and accuracy. Our HVOF process incorporates liquid CO² cooling which offers advantages in process speed, quality and cost. Using this process results in lower porosity, higher density and higher coating hardness when compared to standard air cooled processes. This Cooling System allows us to reduce thermal expansion which in turn reduces tensile stresses on the coatings and increased bond strength.
The extreme velocities involved with the HVOF process produce coatings with an extremely strong bond strength and in many cases will actually impregnate the base metal. In order to provide a complete components, B&B will carry out a range of finishing processes in house. This includes Grinding, Lapping, Sealing and arrangement of Heat Treatment.