Influence of solution heat treatment on microstructure and stress rupture properties of a Ni₃Al base single crystal superalloy IC6SX

The effect of solution heat treatment at different temperatures on the microstructure and stress rupture properties of a Ni₃Al base single crystal superalloy IC6SX has been investigated in this paper. The experimental results show that the as-cast alloy exhibited a typical dendritic structure with three phases of γ′, γ and NiMo. After solution heat treated at 1240 °C, the NiMo phase dissolved entirely. With the temperature increasing, the γ′ phase in interdendritic region dissolved earlier than that in dendritic region. When solution heat treatment temperature reached to 1280 °C, all of the γ′ solutioned and a uniform microstructure was observed. Furthermore, increasing the temperature up to 1340 °C, a small amount of incipient melting occurred in the alloy. The stress rupture life of IC6SX at 1100 °C/130 MPa increased with the rising of temperature and reached to the top value under the solution heat treatment temperature of 1280 °C. The optimum solution heat treatment considered to be 1280 °C/10 h followed by flowing air cooling.