Effect of gas temperature on critical velocity and deposition characteristics in kinetic spraying

This study evaluated the effects of particle temperature and substrate material on critical velocity and deposition efficiency in kinetic spraying. A wide range of process gas pressures and temperatures was used in this experiment to vary both particle velocity and temperature. A bronze (Cu–Sn alloy) feedstock was deposited onto aluminum, mild steel and bronze substrates. The experimental results showed that the critical velocity was strongly dependent on the combinations of particle/substrate and particle temperature. The decreasing critical velocity could be obtained at the same particle velocity, due to an increasing particle temperature. In our experiments, the critical velocity decreased by 50 m/s when the process gas temperature increased by 100 8C. When process conditions are optimized to have good bond strength and deposition efficiency, two critical velocities must be considered; one is that of the particle deposition onto the substrate (Vcr1) and the other is that of particle–particle bonding (Vcr2).