Different roles of stacking fault energy and diffusivity in the creep performance of nickel-based single-crystal superalloys

Two nickel-based single-crystal (SC) superalloys (designated T6 and T13) were investigated in order to reveal the effects of stacking fault (SF) energy and diffusion on their high-temperature creep behavior. In this study, the effect of dislocation spacing on creep was the same between T6 and T13. The microstructure and deformation rate attained prior to 1% creep were investigated in detail. Several differences were detected in the two superalloys, the reasons for these differences were discussed. The results suggested that the SF energy of the γ matrix was the key factor affecting development of the dislocation network. Because the matrix of the T6 superalloy has lower SF energy than T13, the cross-slipping of dislocation was more difficult in the early stages of creep, which resulted in lower levels of dislocation propagation and of formation of the dislocation network. When creep had entered the steady stage, the key process controlling high-temperature creep was atomic migration in the γ matrix, and the creep rupture life was lengthened by reducing the penetration of dislocations into the γ′ raft and slowing down its topological inversion.