Abstract: The microstructure degradation of K465 high-pressure turbine blades after (1150-1310) ℃× 15 min of over-temperature heat treatment was studied. The results show that the macroscopic grain color gradually changes from yellow,dark yellow+light blue to dark blue with the increase of over-temperature temperature.The interdendrite and dendrite γ' phase,the carbide γ' film,and the grain boundary γ' film are dissolved at 1240 ℃,1250-1260 ℃ and 1270 ℃,respectively.The initial melting of eutectic occurs at 1280 ℃,and when the temperature increases to 1310 ℃,the eutectic phase is dissolved and the basket-like morphology is precipitated again after air cooling. The degeneration of carbide structure is mainly manifested by the dissolution of γ' film and the re-dissolution of M₆C. The degradation of grain boundary structure is mainly manifested by the dissolution of γ' film and the occurrence of initial melting. With the increase of temperature,the evolution of the interdendrite and dendrite γ' phase from merging,spheroidization,dissolution to re-precipitation of fine globules happens,and the area fraction of γ' phase decreases.