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Haynes, J. A.; Zemskova, S. M.; Lin, H. T.; Ferber, M. K.; Westphal, W.
Journal of the American Ceramic Society, November 2006, Letnik: 89, Številka: 11Journal Article
Silicon nitride ceramic vanes coated with chemical vapor‐deposited (CVD) mullite, CVD alumina, and plasma‐sprayed tantalum oxide were exposed to field tests in an industrial gas turbine engine. Results varied due to expected non‐uniformities in the CVD coating microstructures, but dense CVD mullite/alumina showed excellent stability and protective capacity after 1148 h of engine testing. Surfaces without CVD coatings experienced massive intragranular subsurface oxidation and/or rapid recession of the ceramic substrate due to volatilization of silica species formed by oxidation. These results suggest that thin (<5 μm), dense, high‐purity CVD mullite and CVD alumina are viable components for an environmental barrier coating system to protect structural ceramics in combustion environments.
