Unique performance of thermal barrier coatings made of yttria-stabilized zirconia at extreme temperatures (>1500°C)

Vaßen, R. and Mack, D.E. and Tandler, M. and Sohn, Y.J. and Sebold, D. and Guillon, O.

Volume: 104 Pages: 463-471
DOI: 10.1111/jace.17452
Published: 2021

Yttria-stabilized zirconia (YSZ) has been for several decades the state of the art material for thermal barrier coating (TBC) applications in gas turbines. Although the material has unique properties, further efficiency improvement by increasing the temperature is limited due to its maximum temperature capability of about 1200°C. Above this temperature the deposited metastable tetragonal (t´) phase undergoes a detrimental phase transformation as well as enhanced sintering. Both processes promote the failure of the coatings at elevated temperatures and this early failure has been frequently observed in gradient tests. In this paper, we now experimentally shown for the first time that under typical cycling conditions not the time at elevated temperatures leads to the reduced lifetime but the transient cooling rates. If cooling rates were reduced to 10K/s, TBC systems could be operated in a burner rig at a surface temperature well above 1500°C without showing a lifetime reduction. The explanation of these astonishing findings is given by the evaluation of energy release rate peaks during fast transient cooling in combination with the phase evolution during cooling with the used cooling rates. © 2020 The Authors. Journal of the American Ceramic Society published by Wiley Periodicals LLC on behalf of American Ceramic Society (ACERS)

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