Transport and deposition behaviors of vapor coating materials in plasma spray-physical vapor deposition

Abstract

The plasma spray-physical vapor deposition (PS-PVD) technology offers great potential to support the development of non-line-of-sight deposition. However, many researches indicated that the shadowing effect is a significant mechanism of PS-PVD for the coating growth and formation of the micro-structure. There seems to be an irreconcilable contradiction between the two theories. In this study, both the transport and deposition behavior of PS-PVD processes are researched from a macroscopic and microscopic perspective, respectively. The deposition processes of vapor coating materials are separated by the last collision position. The process before reaching the last collision position is defined as transport behavior, and the process after the last collision position is defined as deposition behavior. The results of simulation and experiment indicated that the flow behavior of plasma jet and the frequent collisions between plasma gas and vapor coating material provide opportunities for the vapor coating material to deposit in shadowed surfaces or non-line-of-sight positions. The shadowing effect under micro line-of-sight deposition is a major factor in the growth of columnar structures, and it accompanies the entire process of coating growth. This study divides the deposition process of vapor coating materials into the macro non-line-of-sight transport and micro line-of-sight deposition, illuminates the macro-non-line-of-sight transport behavior of vapor-phase materials, and sheds light upon the micro-line-of-sight deposition mechanism of the PS-PVD process.