Accessible Requires Authentication Published by De Gruyter June 11, 2013

Internal stresses and phase stability in multiphase environmental barrier coatings

K. T. Faber, C. M. Weyant, Bryan Harder, Jonathan Almer and Kang Lee

Abstract

The use of silicon-based ceramics in power generation applications is limited by recession of the passivating SiO2 when it reacts with water-vapor to form a volatile hydroxide. Environmental barrier coatings are used to prevent diffusion of reactive species to the structural ceramic substrate. Often these barriers are multilayered and/or multiphase to provide optimal thermal expansion match, microstructural stability, as well as low diffusivities. High energy X-rays are used to assess internal stress as well as phase content and stability in two coating systems: alloyed Ta2O5 for Si3N4 and strontium-aluminosilicates for SiC/SiC. In particular, the role of phase transitions and precipitation on the coating internal stresses is evaluated along with their ramifications for coating lifetime.


* Correspondence address, Professor Katherine T. Faber, Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208 USA. Tel.: +1 847 491 2444, Fax: +1 847 491 7820, E-mail:

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Received: 2007-6-25
Accepted: 2007-9-4
Published Online: 2013-06-11
Published in Print: 2007-12-01

© 2007, Carl Hanser Verlag, München