In situ SEM study of creep deformation behavior of nickel-based single-crystal superalloys

This study aimed to compare the dynamic microstructure evolution and the creep mechanical properties of second-generation nickel-based single-crystal superalloys at 780 °C/720 MPa and 850 °C/720 MPa. A method based on in situ scanning electron microscopy creep testing was used to identify the occurrence of slip bands. At the same time, the deformation mechanisms at 780 °C and 850 °C were discussed. The creep life at 780 °C was longer, almost five times that at 850 °C. Moreover, significant necking occurred in the primary creep at 780 °C, which controlled the entire creep process and accounted for almost 50% of the total life. In comparison, the primary creep at 850 °C was obviously shortened, mainly showing the characteristics of the second and third stages; the necking was mainly concentrated in the later stage of creep. This difference must be caused by the dislocation motion. The slip deformation mainly occurred at 780 °C, and the < 112 > dislocations shearing γ′ strengthening phase left obvious slip bands on the surface. The dislocations moved in the matrix channel in the early stage of creep at 850 °C, and the dislocations sheared γ′ strengthening phases in the later stage of creep while leaving obvious slip bands on the surface.