High temperature interactions between environmental barrier coating (EBC) ceramics and calcia-magnesia-alumina-silicate (CMAS) glass
June 24-29, 2018
Ceramic-matrix-composites (CMCs) are being researched to replace current metallic hot-section components, which would allow for higher operating temperatures. Due to the oxidation of CMCs (usually SiC-based) in the presence of water vapor, dense environmental barrier coatings (EBCs) are needed. At temperatures above 1200 °C, silicate particles (sand, volcanic ash, fly ash, etc.) enter the engine, melt on the hot surfaces and form calcia-magnesia-alumina-silicate (CMAS) glass deposits. The molten CMAS glass can penetrate grain boundaries and cause dissolution, which leads to premature failure. New coatings are needed to protect CMCs from CMAS attack.
A new model, based on optical basicities, has been used to predict the reactivity between CMAS and potential EBC ceramics. Based on this analysis, several potential EBC ceramics have been identified: yttrium aluminate (YAlO3), yttrium disilicate (g-Y2Si2O7), ytterbium disilicate (b-Yb2Si2O7), and scandium disilicate (b-Sc2Si2O7).
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Laura R. Turcer, Hector Garces, Lin Zhang, Nitin P. Padture, and Amanda R. Krause, "High temperature interactions between environmental barrier coating (EBC) ceramics and calcia-magnesia-alumina-silicate (CMAS) glass" in "Thermal Barrier Coatings V", Prof. Dr. Robert Vaßen, Forschungszentrum Jülich GmbH, Germany Brian Hazel, Pratt & Whitney, USA Prof. Dr. Uwe Schulz, German Aerospace Center, Germany Dr. Michael J. Maloney, Pratt & Whitney, USA Dr. Ram Darolia, GE Aviation (Retired), USA Eds, ECI Symposium Series, (2018). http://dc.engconfintl.org/tbcv/23