Influence of Melt Superheating Treatment on Solidification Microstructure and Mechanical Properties of Ni-Based Superalloy GH742

The melt superheating treatment was carried out for reverted GH742 superalloy. Under the same solidification conditions, the microstructure evolution and its influence on mechanical properties was investigated by changing the melt superheating temperature. The results show that the grain and dendrite are refined, and the dendrite segregation and the contents of N, O and S are decreas ed with the melt superheating temperature increasing from 1450 °C to 1550 °C. However, the grain and dendrite becomes coarse, dendrite segregation becomes serious and the contents of N, O increase after the melt superheating treatment at 1600 °C. The morphology of MC carbide is rod-shaped or blocky. The melt superheating treatment has no significant influence on the morphology of MC carbide, but slightly decreases its size and area fraction. With increasing melt superheating treatment temperature, γ′ morphology changes from near-sphere to cube, but γ′ size first reduces with the increase of melt superheating temperature between 1450 °C and 1550 °C, but increases when the superheating temperature is higher than 1550 °C. Corresponding to this, the tensile strength at room temperature is significantly improved after melt superheating treatment at 1550 °C, but the ductile has no obvious change. © 2022 Rare Metals Materials and Engineering Press. All rights reserved.