Solid-state deposition in which nitrogen or helium, heated and pressurized, accelerates powder through a converging-diverging nozzle to roughly 500 to 1,200 m/s. Particles never melt; they deform violently on impact and bond once they exceed a critical velocity. Deposits are dense, pick up no oxide in flight and sit in compressive stress, and they can be built thick for repair or additive work. It suits ductile metals such as aluminum, copper, nickel, titanium and tantalum.
Corrosion pits on the magnesium gearbox housing go to cold spray, aluminum powder, no heat to worry about.
Soft metals like aluminum tend to stick and clog the diverging section of the nozzle, so nozzle material and gas temperature are picked to keep it clear as much as to hit velocity.
Also heard as
- cold gas dynamic spray
- kinetic spray
- supersonic particle deposition
Related terms
Critical velocity
The minimum impact speed a cold spray particle needs to stick to the surface instead of bouncing off.
Deposition efficiency
The percentage of the feedstock sprayed that actually ends up as coating on the part.
Residual stress
Stress locked into a coating and substrate after spraying, from splat shrinkage, cooling and impact.
Dimensional restoration
Rebuilding worn or mis-machined surfaces to original size with thermal spray, then machining to finish.