No abstract

Duplex Zr02-8 wt % Y2O3/Ni-22Cr-1OAI-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)204 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. [