Effect of carbon addition on microstructure and mechanical properties of a typical hard-to-deform Ni-base superalloy

In this paper, the as-cast microstructure, microsegregation, and mechanical properties of GH4151 superalloys with a carbon addition were studied by scanner electron microscopy (SEM), transmission electron microscope (TEM), electron probe microanalysis (EPMA), differential thermal analyzer (DSC), and electron backscattered diffraction (EBSD). The results show that the solid solution effect of carbon in alloys is limited, the addition of C from 0.01 to 0.08 ​wt% significantly refines the secondary dendrite spacing(SDAS) from 61.7 to 57.4 and 51.8 ​μm. Due to the influence of thermal solutal convection, the most severe segregation is found in the C-0.04 alloy, and the solidification ranges of C-0.01, C-0.04, and C-0.08 alloys are 87 ​°C, 96 ​°C, and 83 ​°C, respectively. Owing to the reduced solidification pores and formed finely dispersed carbides, C-0.04 shows excellent ultimate tensile strength (442 ​MPa) and superior total elongation (1.368%) at 1100 ​°C much better than that of C-0.01(130.7 ​MPa, 0.085%) and C-0.08(248 ​MPa, 1.026%).