Evolution of γ′ precipitates in GH4742 superalloy based on complete forging-heat treatment process

The temperature changes at the rim, 1/2 radius, and bore of the turbine disk during the solution treatment were measured. Based on the measured temperature data, solution treatment experiments with different cooling rates (14, 51, and 93 °C/min) were performed, and the solution temperatures were 1120 and 1080 °C. At all three cooling rates, the multimodal size distribution of γ′ precipitates was detected, and the size of γ′ precipitates is inversely related to the cooling rate. Only the secondary and tertiary γ′ precipitates were found at a solution temperature of 1120 °C, and the secondary γ′ precipitates progressed from spherical (93 and 51 °C/min) to flower-like (14 °C/min) shape, with the flower-like γ′ precipitates regulated by aggregation. At a solution temperature of 1080 °C, the γ′ precipitates evolve from cuboids (93 and 51 °C/min) to irregular shapes (14 °C/min). Irregular γ′ precipitates are affected by the lattice mismatch between the matrix and the γ′ precipitates.