Independent Control of Particle Temperature and Velocity using a Novel Powder Preheater Design for Low Pressure Cold Spray

In high-pressure cold spray, the enthalpy of the particle carrier gas has a significant effect on the propellant gas conditions and ultimately on particle impact velocities and temperatures. Through modelling and experimentation, the current work demonstrates that in low-pressure cold spray, the particle carrier gas enthalpy has a minimal effect on the particle velocity and is rather limited to affecting the particle impact temperature. Consequently, particle impact temperature can be controlled independently from impact velocity. This is a valuable tool when dealing with temperature sensitive substrates: low propellant temperatures can be used in combination with high carrier gas temperatures enabling particle deformation while minimizing substrate heat input.

Particle preheating was used to inject pure aluminum particles in a commercial low-pressure cold spray to temperatures up to 500°C. This was accomplished without clogging because of the development of a novel particle preheater, which eliminated the particles exposure to hot metal surfaces. Even after substantial spray time, no evidence of wear or clogging was found. The particle preheating resulted in a deposition efficiency increase of 3.6 times when compared to the injection of room temperature particles, while particle impact velocity was kept constant due to the possible decoupling in low-pressure cold spray.