Design of Solution Treatment for High-Generation Single-Crystal Superalloys with Enhanced Refractory Content

Increasing the fractions of certain refractory elements resulted in the development of modern single-crystalSingle-crystal superalloysSuperalloys with not only improved high-temperatureHigh temperature performance but also increased solidificationSolidification segregationSegregation of elements. The importance of solution treatment to reduce segregationSegregation and homogenize the microstructureMicrostructure has been well verified; however, guidelines for achieving simple but effective homogenization practices have yet to be developed. In this study, the effects of different solution treatments on the creep propertiesCreep properties of a fourth-generation single-crystalSingle-crystal superalloySuperalloys were investigated, and two guidelines for designing homogenization practices for modern single-crystalSingle-crystal superalloysSuperalloys were proposed. First, the degree of homogenization achieved by solution treatment will be saturated once the dendritic segregationSegregation coefficient of specific elements reaches a certain limit (lower than 1.2 for Re and W, and higher than 0.9 for Al and Ta). Second, if the residual segregationSegregation is strong, different degrees of local deformations between the dendrite core (D) and interdendritic (ID) regions induce uneven fractures in the alloy. An effective, fully homogenized structure should exhibit similar local strengths in the D and ID regions. These guidelines will help assess the effectiveness of solution treatments and guide the development of new solution treatment strategies for modern single-crystalSingle-crystal superalloysSuperalloys.