The Effect of Heat Treatment on the Microstructure of Cast Ni-based IN100 Superalloy

The purpose of this study was to investigate the effect of heat treatment including solution treatment and aging on the microstructure of cast nickel-based IN100 superalloy including size, volume fraction and morphology of primary γ' and different kinds of carbides. For this purpose, different solution heat treatment cycles and a constant aging cycle were implemented on cast ingot samples and the microstructure of the samples were analyzed by scanning electron microscopy and optical microscopy. It was found that, the alloy in the full partial aging treated condition had the optimal combination of γ' morphology, volume fraction and size. In this condition, the alloy possesses a cubic primary γ' with 45% volume fraction which is a significant increase as compared to other cycles. Discrete M_23 C_6 carbides were formed at the grain boundaries and the morphology of the cubic MC carbide was changed to the spherical shape.