Abstract: Effects of solution treatment temperature and time on microstructure and mechanical properties of a novel nickel-cobalt-based superalloy were studied by means of OM, SEM and tensile test. The results show that the evolution of the grain size is consistent with the change of the primary γ′ phase volume fraction. When the solution treatment temperature is below 1110 ℃, the grain size increases slowly with the increase of solution treatment temperature or time due to the grain boundaries pinning effect caused by the residual primary γ′ phase. When the solution treatment temperature is 1110 ℃, the primary γ′ phase is basically redissolved as the solution treatment time increases to 4 h, which results in a rapid increase of grain size. With further extending the solution treatment time to 6 h, the increase of grain size slows down, the temperature for full dissolution of the γ′ phase in the tested alloy is 1110 ℃. In addition, after solution treatment at 1100 ℃ for 4 h and two-stage aging treatment (670 ℃×24 h, air cooling and 780 ℃×16 h, air cooling), the tensile strength and yield strength of the alloy reach the maximum value, 1584 MPa and 1104 MPa, respectively. Thus, the optimal solution treatment of the tested alloy are confirmed as at 1100 ℃ for 4 h, respectively.

Key words: solution treatment, novel nickel-cobalt-based superalloy, microstructure, mechanical properties