High-velocity oxygen fuel spraying, in which kerosene, hydrogen, propylene, propane or natural gas burns with oxygen in a pressurized chamber and exits through a converging-diverging nozzle as a supersonic jet. Powder reaches roughly 400 to 800 m/s while staying relatively cool, giving dense, tightly bonded coatings with porosity often under 1 percent. It is the main process for tungsten carbide and chromium carbide wear coatings and for hard chrome replacement.
HVOF the landing gear pins with WC-CoCr, 0.012 on, and send them to diamond grind.
Liquid-fuel guns handle coarse powders and give heavier peening, while gas-fuel guns run finer powders; sprayers rarely swap one for the other without requalifying.
Also heard as
- high-velocity oxygen fuel
- high-velocity oxy-fuel
- HVOF spray
Do not mix it up with
- HVAF: HVOF burns fuel with pure oxygen, while HVAF uses compressed air, which runs cooler and is cheaper to operate.
Related terms
HVAF
High-velocity air fuel: an HVOF-style process that burns fuel with compressed air instead of oxygen.
WC-Co
Tungsten carbide in a cobalt binder, the most common wear-resistant thermal spray coating.
Barrel
The long tube on an HVOF or detonation gun where particles are heated and accelerated before exiting.
Hard chrome replacement
Using HVOF carbide coatings in place of electroplated hard chrome on rods, pins and landing gear.
Detonation gun
Process that fires powder from a long barrel using repeated explosions of oxygen and acetylene.