Effect of carbon additions on hot tearing of a second generation nickel-base superalloy

The effect of carbon (C) additions on hot tearing susceptibility in high-refractory nickel-base superalloy CMSX-4 was explored. It was found that minor additions of C lead to a reduced hot tearing tendency in the second generation nickel-base alloy. The C additions vary the volume fraction and distribution of the γ/γ′ eutectic due to the formation of carbides. In the C-containing alloys, the volume fraction of eutectic is reduced and the eutectic is present in the form of isolated pools in the interdendritic region of the dendrite structure. The hot tearing is associated with formation of continuous eutectic films. We assume that the eutectic, which reflects the remaining liquid at the end of solidification, prevents the impinging dendrite arms from bridging and in this way decreases strength of the forming solid.