Effects of Gun Scanning Pattern on the Structure, Mechanical Properties and Corrosion Resistance of Plasma-Sprayed YSZ Coatings

Due to the non-symmetric distribution of sprayed particle plume in conventional plasma spraying caused by the radial injection of feedstock powder into a plasma jet, significant influence of the gun scanning pattern can appear in the structure of the 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 patterns of an air plasma spray gun were adopted with a commercial ZrO2-8 mass% Y2O3 (YSZ) powder. The cross sections of the obtained YSZ coatings were observed by SEM, while interfacial fracture 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.