Effects of rejuvenation heat treatment on microstructure and creep property of a Ni-based single crystal superalloy

Both surface and internal microstructures of a second-generation Ni-based single crystal (SX) superalloy were studied after creep and rejuvenation heat treatment (RHT). It is indicated that the microstructures, such as the dislocation network, the γ phase and the γ' phase, can be recovered to those after the standard heat treatment (SHT). It is found that RHT affected zone (RAZ) formed at the surface is composed of the γ'-free layer, the transition layer and the recrystallization (RX), which are less than 20 μm in depth totally. Such depth of the RAZ doesn’t affect the properties of the superalloy. The morphology of γ' phase at the RAZ is related to the composition of the elements. The average creep life after RHT is close to the average life after SHT. It is concluded that RHT could effectively repair SX parts and increase the total life of the sample after a damage by creep.