Abstract:The microstructure, the thermal deformation behavior and the microstructure evolution during the thermal deformation of a novel Ni-based Powder Metallurgy(PM) superalloy under different initial conditions（1150℃ Hot Isostatic Pressing，1150℃ Hot Isostatic Pressing+1150℃ Hot Extrusion，1150℃ Hot Isostatic Pressing+1130℃ Hot Extrusion）were investigated by means of the Scanning Electron Microscope(SEM), the Optical Microscope(OM), the Thermal Compression Testing Machine, and the Electron Backscatter Diffractive (EBSD). The results show that the PPBs and the coarse γ′still remains in the HIP samples and the PPBs disappeared in the 1130℃ and 1150℃ hot Extrusion samples, which are equiaxed Grains. During the thermal deformation process, the Work Hardening-Recrystallization Softening phenomenon was observed in these three samples under different conditions. The thermal deformation activation energies of peak stress are 861kJ/mol, 858kJ /mol and 489kJ/mol, respectively. The deformation temperature had an obvious effect on the deformation microstructure of the samples. The abnormal grain growth appeared in both the hot isostatic pressing and hot isostatic pressing+1130℃ hot extruded samples under the condition of 1150℃-0.001/s. Compared with the other two conditions, the sample of 1150℃ Hot Isostatic Pressing+1130℃ Hot Extrusion showed the best deformation behavior.