The effect of long-term thermal exposures on the microstructure and properties of CMSX-10 single crystal Ni-base superalloys

The long-term thermal stability of CMSX-10 single crystal superalloys has been studied as a function of heat treatment and thermal exposure. The CMSX-10 alloys were subjected to long-term unstressed heat treatments at temperatures of 950 and 1050 °C for periods of 1000 and 10,000 h. The microstructures and creep properties of the samples before and after long-term thermal exposures were characterized. The γ′ coarsening was observed after all exposures and the formation of topologically close packed (TCP) phases was observed in both samples exposed at 1050 °C and the 10 kh exposure at 950 °C. High temperature creep tests were carried on these samples at 950 °C at an engineering stress of 310 MPa. The creep lives were found to deteriorate with the increase in exposure time and temperature as a result of the microstructural degradation. The coarsening of the γ′ precipitates was observed to be the main factor in the degradation of the properties.