| Abstract Scope |
All materials of current interest for the hot section of advanced gas turbines require protective coatings to survive in extreme environments involving temperatures ≥1200°C, pressures ≥30 bar, high velocity moisture-laden combustion gases and multiple contaminants, especially siliceous debris ingested with the intake air. The coatings generally involve two or more layers designed to provide thermal insulation as well as protection against environmental attack including oxidation, moisture-enhanced volatilization, as well as penetration and/or dissolution by silicate glassy melts generically known as CMAS. This presentation will discuss the role of phase diagrams and Calphad tools in understanding problems of phase stability, interdiffusion and thermochemical interactions with extraneous deposits, as well as the ensuing thermomechanical effects, using examples from thermal and environmental barrier coatings. A major challenge is presented by increasing chemical complexity of the systems, which may involve stacks of multiple coating materials, with melts containing at least five relevant chemical species. |