Significant influence of carrier gas temperature during the cold spray process

Carrier gas is known as the medium to inject the cold sprayed powders into the main driving flow inside the nozzle. Hence, the properties and conditions of carrier gas should be of great importance to the particle motion behaviour and then particle deposition process. In this study, the effect of carrier gas temperature on the particle acceleration and deposition in cold spray process was investigated by both numerical and experimental methods. It is found that the supersonic driving gas flow and the consequent particle acceleration behaviour are significantly influenced by the carrier gas temperature, more specifically, higher carrier gas temperature results in higher particle impact velocity. In addition, because the carrier gas has additional heating effect on the powder particles before injection, the final impact temperature also increases with the carrier gas temperature, which leads to the reduction in the critical velocity. The increase in particle impact velocity and reduction in critical velocity enable the deposition efficiency and coating bonding strength to significantly improve as the carrier gas temperature increases. The particle impact velocity is found to be more influential than critical velocity reduction.