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.