Design of Thermally Reliable Environmental Barrier Coating for a SiC/SiC Ceramic Matrix Composites

Abstract

Silicon carbide-fiber-reinforced silicon carbide matrix composites (SiC/SiC CMCs) have been proven to possess greater high-temperature strength and durability. These materials are usually used in air breathing engines due to their unique properties. However, the application of SiC/SiC CMCs is ineffective in combustion environment due to oxidation and surface recession. Efforts to improve service of SiC/SiC CMCs in combustion environments require knowledge of their long-term stability in combustion environments, volatility, phase stability, and thermal conductivity. Therefore in this paper, the design of a reliable EBC for SiC/SiC CMCs with excellent corrosion, recession and thermal shock resistance is proposed. This design consists of a three-multilayer; yttrium disilicate/mullite/ytterbium disilicate (Y2Si2O7/ 3Al2O3.2SiO2/Yb2Si2O7) system. Also, finite element models (FEMs) were used to predict the thermal residual stresses within the proposed multilayers under operating conditions. The implications of the results are discussed for potential application of this EBC system in air breathing engines.