Study of microstructure degradation and rejuvenation evolution for F-class gas turbine blade

Service degradation of F-class gas turbine blade and its microstructure evolution during a simple rejuvenation process are investigated, and then microhardness of the rejuvenated blade is evaluated. The results show that the turbine blade suffers from significant service degradation such as spheroidising, coarsening and rafting of the γ′ phase. It is also verified that the γ′ precipitates microstructure could be recovered and even improved by a full solution followed by two-step aging. The proper solution temperature is necessary to dissolve the deformed γ′ precipitates and allows optimum reprecipitation during next aging. The microstructure of the rejuvenated blade all shows bimodal distribution with coarse and fine γ′ precipitates. The microhardness is higher and more uniformly distributed than that of the service-exposed blade.