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

In high-pressure cold spray, it has been demonstrated that the enthalpy of the particle carrier gas has a significant effect on the propellant gas conditions and resulting particle impact velocities and temperatures. Through modeling and experimentation, this study demonstrates that in low-pressure cold spray, the enthalpy of the particle carrier gas has a minimal effect on the particle velocity; therefore, particle temperature can be controlled independently from particle velocity. This is a unique feature of downstream injection and a valuable tool when dealing with temperature sensitive substrates and particles. In this study, particle preheating was used to inject pure aluminum particles up to temperatures of 500 °C, about 80% of their melting temperature. This particle preheating was accomplished without clogging because of a novel particle preheater which eliminated the particles exposure to hot metal surfaces. It was found that even after substantial spray time, there was no evidence of wear or clogging. The preheating resulted in a DE increase of 3.6 times when compared to the injection of room temperature particles.