Effect of Solid Solution Treatment Routes on the Microstructure Configuration of a Third-Generation Ni-Based Superalloy

The step and ramp heat treatments can improve the homogenization degree of the structure in superalloys. However, the comparison between them using the same temperate range and total holding time on the microstructure and the microstructural stability is still vague. The effects of step and ramp heat treatment in the same solution temperature range and the same hold time on the microstructural stability in a third-generation superalloy were studied. The sizes of γ′ phases at dendrite cores and dendrite edges are different, which is caused by the dissolution degree of the γ′ phase during solution treatment. A low degree of γ′ phase dissolution aggravates the dendritic segregation. Dendrite segregation makes refractory elements such as Co, Mo, W, and Re aggregate in the dendrite core, and the TCP phase is easy to nucleate and precipitate during long-term thermal exposure, resulting in decreased structural stability. The investigations in this study compare the differences and obtain optimized processes and parameters for the improvement of superalloys.