Microstructure and stress rupture property of Ni-based monocrystal superalloy with melt superheating treatment

The melt superheating treatment during the directional solidification is carried out for DD3 Ni-based monocrystal superalloy. With the unchanged thermal gradient and withdrawn rate for different melt superheating temperatures, the influence of the melt characteristic on the microstructure and the mechanical property is studied. The results show that the dendrite and the γ′ precipitate are all obviously refined while the γ′ precipitate becomes more regular when the superheating temperature is increased from 1500 °C to 1640 °C and then to 1780 °C. The superheating treatment has no obvious influence on the dendrite segregation of Al, Cr and Co but can reduce the dendrite segregation degree of W, Mo and Ti. With the elevated superheating temperature, the γ′ rafts become more stable and the stress rupture property under 1040 °C/190 MPa is improved.