The effects of process parameters on mechanical property and visual aspect of plasma sprayed Y203 coating

Abstract

The effects of process parameters on the mechanical property and visual aspect of Y203 coating formed by plasma spraying were investigated. For the experiments, granular Y203 powders were plasma sprayed using plasma gun with external powder-feeding system. When an asymmetric spraying was introduced by one-side powder-feeding, bigger pores and more frequent black spots were found in the region formed in opposite side from powder feeding direction, where the droplets of relatively lower temperature and lower flying velocity impinged to form coating. The optimum conditions for highest Vickers hardness were found to be different from those for white visual aspect of the Y203 coatings. Among the process parameters such as Ar flow rate, H2 flow rate, 02 contents, spraying distance, spraying distance was known to be most important for the formation of black spots in Y203 coating. The black spots formed in Y203 coating are thought to have relationship with the breakdown of stoichiometry between Y and O during plasma spraying. Consequently, the processing route not to form black spots in Y203 coating is described.