Effects of Gun Scanning Pattern on the Structure and Corrosion Resistance of Plasma Sprayed YSZ Coatings

Due to the non-symmetric distribution of sprayed particles plume in conventional plasma spraying caused by the radial feeding of feedstock powder, significant influence of scanning pattern can appear in the structure of sprayed coatings. Especially the portion of poorly treated powder flux can be a cause of horizontal cracking as well as poor coating adhesion. In this study, three different scanning patters of an APS plasma gun were adopted with a commercial YSZ powder. The cross sections of the obtained YSZ coatings were observed by SEM while interfacial toughness was measured by the indentation method and hot corrosion testing was conducted. It was found that by modification of the gun scanning pattern, it is possible to decrease the possibility of horizontal weak bonding between spray passes and improve the coating adhesion and corrosion resistance.