Hardfacing HVOF:

Some components (above all valves) can be supplied with thermal spray techniques HVOF (high velocity oxy fuel). This technology allows a reduction of the oxidation of particles during the operation. The high velocity of fuel guarantees that the particles, especially those not completely fused, are deformed with the impact on the substratum, thus reducing the porosity of the coating and increasing the adhesion. This operation makes the treated products wearproof, even under heavy loads and high temperatures. Raw spray hardfacings are usually grounded.
Little parts of bars, bushes and other minor valves components are normally treated. The most common fuel used for the mixture is composed of chrome carbides, nickel, cobalt, or alloy cobalt (stellites), or other typical alloys patented by each manufacturer.