Effect of Interlayer on Flatness and Adhesion of Aerosol-Deposited Yttrium Oxide Coating

In this study, Y₂O₃ coating is used as an interlayer between Al₂O₃ substrate and a ceramic coating; this is in order to minimize the morphological distortion produced by a single deposition of the ceramic coating on the Al₂O₃ substrate, which is performed using the aerosol method. The interlayer coating, which comprises the Y₂O₃ phase, is deposited on the Al₂O₃ substrate using an e-beam evaporator. The crystal structure of the powder that was used to process the coating is identified as cubic Y₂O₃. In contrast, the crystal structure of the top-coating layer and interlayer indicates the presence of two kinds of Y₂O₃ phases, which possess cubic and monoclinic structures. The single Y₂O₃ coating without an interlayer exhibits microcracks around the interface between the coating and the substrate, which can be attributed to the stress that occurs during aerosol deposition. In contrast, no cracks are found in the aerosol-deposited Y₂O₃ coating and interlayer, which show a desirable microstructure. The single Y₂O₃ coating and the Y₂O₃ coating with an interlayer exhibit similar hardness and elastic modulus values. Nevertheless, the Y₂O₃ coating with an interlayer exhibits a higher level of adhesion than the single Y₂O₃ coating, with a value of 14.8 N compared to 10.2 N.