Threshold velocity in cold spray above which a particle deforms enough on impact for its surface oxide to break up and metallic bonding to occur, through intense localized shear at the interface. It depends on the material, particle size, oxygen content and particle temperature, and typically falls in the range of 500 to 900 m/s for common metals. Deposition efficiency climbs steeply once most of the powder exceeds it.
Half the powder is under critical velocity, that's why DE is 40 percent, crank the gas temp or switch to helium.
Also heard as
- Vcr
Related terms
Cold spray
Process that fires solid metal powder at supersonic speed so it bonds by impact rather than melting.
Deposition efficiency
The percentage of the feedstock sprayed that actually ends up as coating on the part.
Feedstock
The raw coating material fed into a thermal spray gun, as powder, wire, rod, cord or liquid suspension.