Performance of EB-PVD Y-based EBC System under High Temperature Water Vapor Environment

Abstract

Environmental barrier coatings (EBCs) based on rare earth disilicate (REDS) are used to enhance the durability of ceramic matrix composites (CMC) in high-pressure, high gas, and velocity combustion atmospheres. While the use of RE-monosilicates, REDS, or multi-component for EBC or T/EBC (thermal environmental barrier coatings) is still under debate, efforts are required to produce dense, uniform, crack-free layers that have good adherence with the Si-bond coat. Thermal spray techniques like atmospherically plasma spray (APS) are the most used to deposit EBCs. APS provides a relatively dense coating, however, most REDS sprayed lose silica and lead to the presence of REDS and REMS mixture. Also, the CMC substrate requires grit blasting, which can damage the matrix and/or fibers. Physical vapor deposition, e.g., magnetron sputtering or electron beam physical vapor deposition (EB-PVD), can provide good control of chemistry, adhesion, and microstructure to improve the accommodation of CTE, without grit blasting the CMC. This study aims to deposit double layer YMS/YDS on SiC substrate using EB-PVD and evaluated their performance at 1350 and 1400°C under 30%m H2O. Results showed dense EB-PVD EBC layers closed to the nominal stoichiometries of YMS and YDS. The changes after the water vapor test will be discussed in terms of morphology, crystalline phase, and chemistry of the coating.