Oxidation performance of PVD Y/Yb environmental barrier coatings under water vapor

Abstract

Environmental barrier coatings (EBCs) are proven to protect SiC-based materials against water vapor in gas turbine environments. The current EBCs are typically comprised of two layers, ytterbium disilicates (YbDS) and a Si bond coat, and are applied by atmospherically plasma spraying (APS) method. YbDS offers high-temperature phase stability, however, it still experiences a detrimental volatilization rate under high velocity steam environment. Yttrium disilicate (YDS) on the other hand exhibits better water vapor resistance but lacks the high temperature phase stability. Combining both properties, Y/Yb disilicates might be very effective as EBCs. This study aims to produce a multi-component EBC system using Electron beam physical vapor deposition (EB PVD) Si bond coat and magnetron sputtering (Y,Yb) silicates on a SiC substrate. Further, EBC system has been tested under water vapor environment at high temperatures. Initial results have shown good adhesion between all the layers after deposition and crystallization heat treatment. The evolution of the microstructure after water vapor oxidation tests will be discussed.