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Characterization of Chemical Vapor‐Deposited (CVD) Mullite+CVD Alumina+Plasma‐Sprayed Tantalum Oxide Coatings on Silicon Nitride Vanes After an Industrial Gas Turbine Engine Field Test
Author(s) -
Haynes J. A.,
Zemskova S. M.,
Lin H. T.,
Ferber M. K.,
Westphal W.
Publication year - 2006
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2006.01256.x
Subject(s) - materials science , mullite , chemical vapor deposition , silicon nitride , ceramic , coating , nitride , chromia , composite material , oxide , layer (electronics) , metallurgy , nanotechnology
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.