Effect of C content on microstructure and hot deformation behavior of a Ni-based superalloy

In this work, isothermal compression tests of a Ni-based superalloy were carried out at γ′ sub-solvus (1140 ℃) and γ′ super-solvus (1170 ℃) temperatures under a true strain 0.693. The effect of C contents (0.01 wt%, 0.04 wt% and 0.08 wt%) on the microstructural evolution and hot deformation behavior of the alloy was investigated. The formation of MC carbide is closely related to C content. Besides, the initial grain size decreased slightly with the increase of C content due to the effect MC carbides. During compression deformation at 1140 ℃, the peak stress increased with the increase of C content. When deformed at 1170 ℃, the 0.04 wt% C alloy has the lowest peak stress, because of the acceleration effect on dynamic recrystallization DRX by MC carbides. However, the 0.08 wt% C alloy has the highest peak stress, the dislocation density also increases with the number of MC carbides increase，which caused high working hardening rate and increased the peak stress in 0.08 wt% C alloy. The discontinuous dynamic recrystallization (DDRX) is the dominant mechanism during deformation at 1140 ℃, while the DDRX and continuous dynamic recrystallization (CDRX) occurred at the same time when deformed at 1170 ℃.