HVOFspraying

High-velocity oxy-fuel spraying, or HVOF spraying, is a thermal spray coating process in which finely ground powder feedstock is injected into a high-velocity combustion flame created by burning a fuel gas with an oxidizer. The heated particles are accelerated to high speeds as they exit the nozzle and impact a prepared substrate, forming a dense, adherent coating with low porosity.

In operation, the spray gun mixes fuel and oxygen to produce a controlled combustion jet. Powder is fed into the jet and heated and accelerated before striking the substrate. The resulting coating typically has a lamellar microstructure and strong adhesion due to high particle velocities and rapid solidification. Compared with some other thermal spray methods, HVOF coatings are known for low oxidation of the material, high density, and good bond strength.

Materials commonly used as feedstock include nickel- and cobalt-based alloys, carbide-containing cermets such as WC-Co, aluminum and stainless steel powders, and various steels. HVOF coatings are applied to improve wear resistance, corrosion resistance, erosion resistance, and high-temperature performance. Typical coating thickness ranges from tens of micrometers to a few hundred micrometers, though thicker layers can be produced with multiple passes.

Applications span industries such as aerospace, automotive, oil and gas, and power generation, where durable surface protection is required for components like turbine blades, valves, shafts, and tooling. Advantages of HVOF include dense coatings with strong adhesion and good mechanical properties, while limitations can include high equipment cost, the need for skilled operation, and deposition rates that may be lower than some alternative methods.