Effect of Surface Grain Refinement on Microstructure and Properties of K465 Superalloy

In this paper, the microstructures were studied by OM and SEM, and the tensile and stress rupture properties were tested for K465 superalloy casted by surface grain refinement and conventional technology. The results showed that: Compared to conventional casting, the surface grain size was refined from M-4 to M-9; The secondary dendrite spacing and eutectic content decreased, while the carbide content decreased from 6.18% to 4.36%; The volume fraction of γ′ had no change, the size of γ′ reduced both in core- and inter-dendritic region, and the homogeneity of microstructure improved; The room tensile strength and plasticity both improved. The medium-temperature stress rupture property improved significantly (800 ℃/600MPa), and the high-temperature stress rupture property decreased (975 ℃/225 MPa), which still met the specification. The change of mechanical properties is due to the refinement of the structure.