Phase stability of t′-zirconia-based thermal barrier coatings: mechanistic insights

Authors

Jessica A. Krogstad, University Of California Santa Barbara
Stephan Kramer, University Of California Santa Barbara
Don M. Lipkin, Ge Global Research, One Research Circle, Niskayuna, New York
Curtis A. Johnson, Ge Global Research, One Research Circle, Niskayuna, New York
David RG Mitchell, University of SydneyFollow
Julie M. Cairney, University Of Sydney
Carlos G. Levi, University Of California Santa Barbara

RIS ID

82420

Publication Details

Krogstad, J. A., Kramer, S., Lipkin, D. M., Johnson, C. A., Mitchell, D. RG., Cairney, J. M. and Levi, C. G. (2011). Phase stability of t'-zirconia-based thermal barrier coatings: mechanistic insights. Journal of the American Ceramic Society, 94 (S1), s168-s177.

Abstract

The temperature capability of yttria-stabilized zirconia thermal barrier coatings (TBCs) is ultimately tied to the rate of evolution of the “nontransformable” t' phase into a depleted tetragonal form predisposed to the monoclinic transformation on cooling. The t' phase, however, has been shown to decompose in a small fraction of the time necessary to form the monoclinic phase. Instead, a modulated microstructure consisting of a coherent array of Y-rich and Y-lean lamellar phases develops early in the process, with mechanistic features suggestive of spinodal decomposition. Coarsening of this microstructure leads to loss of coherency and ultimately transformation into the monoclinic form, making the kinetics of this process, and not the initial decomposition, the critical factor in determining the phase stability of TBCs. Transmission electron microscopy is shown to be essential not only for characterizing the microstructure but also for proper interpretation of X-ray diffraction analysis.