M. Dorfman, L. Xie, I. Aguilar, A. Cipitria, S. Paul, I. Golosnoy, Sulzer Metco (US) Inc., Westbury, NY; A. Patel, Carpenter Technologies, Reading, PA; T. W. Clyne, Univeristy of Cambridge, Cambridge, United Kingdom
Thermal barrier coatings (TBCs) are used in advanced gas turbines to protect metallic components against high temperatures. In most commercial applications, zirconia partially stabilized with yttria,
7~8 wt.% Y2O3-ZrO2 (7YSZ), is the material of choice due to its low thermal conductivity and high thermal expansion coefficient. In this study, thermal barrier coatings were sprayed from various 7YSZ feedstock materials that contain different amount of impurities. Processing conditions are the same for all coatings and the as-sprayed coatings exhibit similar microstructure. Sintering resistance and thermal cyclic life of these coatings were investigated and compared.
Factors affecting the appearance of 7~8 wt.% yttria stabilized zirconia thermal barrier coatings were investigated. The coating appearance can be separated into two aspects, darkening and coloring. Coating darkening is related to the retaining of off-stoichiometric zirconium oxide (ZrO2-x) or yttrium oxide (Y2O3-x). Coloring of TBCs is attributed to the existence of impurity oxides.
