Abstract
Cold spray is a promising process to produce high quality metallic coatings without oxidation and phase transformation. In this process, feedstock particles are accelerated by a super-sonic gas flow, then the particles collide and deposit on a substrate surface with solid phase. The super-sonic gas flow forms plate shock wave in front of the substrate, and it affects in-flight behaviors of the particles. This study investigates the influences of plate shock wave on the in-flight behaviors of the particles and coating deposition. The spray distances between the nozzle and the substrate was changed to change the plate shock wave occurence. The gas flow was analyzed by the computational fluid dynamics. The results of the deposition efficiency of the coatings corresponded to the spray distance. From the simulation results, Mach number distributions increased as the nozzle got close to the substrate. On the other hand, the plate shock wave did not occur when the spray distance increased beyond a certain distance. The plate shock wave formation and particle velocity distribution in the gas flow were strongly affected particle flight and deposition behaviors.
