Influence of melt superteating treatment on solidification microstructure and mechanical properties of Ni-based superalloy GH742

Abstract:

The melt superheating treatment is carried out for reverted GH742 superalloy. Under the same solidification conditions, the microstructure evolution and its influence on mechanical properties is systematically 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 decreased 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 decrease its size and area fraction. With increasing melt superteating 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 ℃, but the ductile has no obvious change.