Texture and microstructure of ZrO₂-4mol% Y₂ O₃ layers obliquely deposited by EB-PVD

Observing texture and microstructure growth in coating layers during oblique deposition provides the most fundamental information to optimize the process parameters of the deposition process. In this study, the columnar structure of 4 mol% Y₂O₃ partially stabilized ZrO₂ (YSZ) coating layers produced by electron beam physical vapor deposition (EB-PVD) process was experimentally investigated. Most results could be summarized as a function of vapor incident angle (VIA), α. While a mixture of 〈110〉 and 〈111〉 textured columns was observed in the samples deposited at a low α less than 30°, single 〈110〉 textured columns were observed at a high α (> 30°). Therefore, the 〈110〉 was the preferential crystallographic growth direction under oblique deposition. However, the direction of 〈110〉 did not accord with the geometric growth direction of the columns, which is approximately predicted based on so-called the tangent rule. It is likely that the mismatch between these directions results in the formation of feather-like structure, which has been commonly reported. In addition to crystallographic observation, the porosities in the coating layers were investigated. The tendency of the porosity with the change of VIA qualitatively agreed with the previously reported prediction based on the Monte Carlo simulation method.