Degradation Mechanisms of ZrO 2 –8 wt% Y 2 O 3 /Ni‐22Cr‐10Al‐1Y Thermal Barrier Coatings

Duplex ZrO 2 –8 wt% Y 2 O 3 /Ni‐22Cr‐10Al‐1Y thermal barrier coatings (TBCs) on Mar‐M247 superalloy were tested under different operating conditions within the temperature range 1000° to 1150°C. Results of experiments in this study show that oxidation of bond coatings is the dominant TBC degradation mechanism whereas the operationally induced stresses exert a conjugate effect. The mechanisms of sintering and phase transformation of top coatings do not contribute to failure of TBCs within the temperature range studied. NiO and Ni(Cr,Al) 2 O 4 grown on the surfaces of the bond coatings seem to accelerate spalling of the top coatings along a top coating/bond coating out‐grown oxide interface. However, it is also concluded that the lifetime of TBCs is not directly related to a critical specific weight gain under thermal cycling conditions.