M. R. Dorfman, L. Xie, Sulzer Metco (US) Inc., Westbury, NY; A. Cipitria, S. Paul, I. Golosnoy, Cambridge University, Cambridge, United Kingdom; T. W. Clyne, Univeristy of Cambridge, Cambridge, United Kingdom; W. Chi, V. Srinivasan, State University of New York -Stony Brook, Stony Brook, NY
Thermal barrier coatings are used to protect the metallic components in hot sections of gas turbines and aero engines against high temperature gases. The application of TBCs allows an increase of 100~150 ºC in turbine or engine operation temperature. The increase of operation temperature is directly related to the efficiency improvement of turbines and engines. Therefore, there is a continuing need to increase the operation temperature of turbines and engines, which will expose TBCs to higher temperatures. Currently, 7~8 wt.% Y2O3-ZrO2 (7YSZ) is the material of choice due to its low thermal conductivity and high thermal expansion coefficient. However, when 7YSZ TBCs were exposed to temperatures higher than 1200 ºC, sintering and phase transformation of 7YSZ become significant and thus result in the degradation or even spallation of TBCs. It was found that the content of impurity oxides in 7YSZ , such as SiO2 and Al2O3, has a significant effect on coating sintering resistance and phase stability of 7YSZ. The reduction of impurity content will significantly improve sintering resistance and phase stability of 7YSZ TBCs and thus allow the 7YSZ TBCs to be used at higher temperatures. In this paper, the mechanical and thermal properties of a high purity 7YSZ thermal barrier coating were evaluated and compared to those of TBCs of lower purities.
Summary: Thermal barrier coatings are used to protect the metallic components in hot sections of gas turbines and aero engines against high temperature gases. The application of TBCs allows an increase of 100~150 ºC in turbine or engine operation temperature. The increase of operation temperature is directly related to the efficiency improvement of turbines and engines. Therefore, there is a continuing need to increase the operation temperature of turbines and engines, which will expose TBCs to higher temperatures. Currently, 7~8 wt.% Y2O3-ZrO2 (7YSZ) is the material of choice due to its low thermal conductivity and high thermal expansion coefficient. However, when 7YSZ TBCs were exposed to temperatures higher than 1200 ºC, sintering and phase transformation of 7YSZ become significant and thus result in the degradation or even spallation of TBCs. It was found that the content of impurity oxides in 7YSZ , such as SiO2 and Al2O3, has a significant effect on coating sintering resistance and phase stability of 7YSZ. The reduction of impurity content will significantly improve sintering resistance and phase stability of 7YSZ TBCs and thus allow the 7YSZ TBCs to be used at higher temperatures. In this paper, the mechanical and thermal properties of a high purity 7YSZ thermal barrier coating were evaluated and compared to those of TBCs of lower purities.
