Environmental Degradation of High-Temperature Protective Coatings for Ceramic-Matrix Composites in Gas-Turbine Engines
Journal Article - Open Access
Brown University Providence United States
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The need for higher efficiencies and performance in gas-turbine engines that propel aircraft in the air, and generate electricity onland, is pushing the operating temperatures of the engines to unprecedented levels. Replacing some of the current hot-sectionmetallic components with ceramic-matrix composites CMCs is making that possible. A high-temperature ceramic coatings system,that includes environmental-barrier coatings EBCs, are needed to protect CMCs. However, these coatings undergo degradation inthe highly hostile environment of the gas-turbine engine consisting of a combination of high gas temperatures, pressures, andvelocities. In addition, there is the ubiquitous presence of steam a combustion by-product and occasional ingestion of calciamagnesia-aluminosilicates CMASs in the form of dust, sand, or ash from the environment. Steam can cause corrosion of EBCs, andthe molten CMAS deposits can react with the EBCs resulting in their failure. This article provides a perspective on the understandingof these degradation mechanisms, and possible approaches, guided by that understanding, for mitigating the degradation. Anoutlook on the future challenges and opportunities is presented.
- Ceramics, Refractories and Glass