Effect of temperature and stress on the creep deformation mechanism of a novel wrought superalloy GH4151

The creep behavior and deformation mechanisms of GH4151, a newly developed heavily alloyed wrought nickel-based superalloy designed for next-generation aero-engine turbine disks, were systematically investigated across a broad temperature–stress window (700–800°C, 480–800 MPa). Microstructural characterization reveals that the dominant deformation mechanisms transition systematically, primarily driven by a temperature-induced reduction in the matrix stacking fault energy. At 700°C, creep deformation is accommodated by a mixed mode of antiphase boundary (APB) shearing and Orowan bypassing. As the temperature increases to 750°C, deformation shifts to extensive microtwinning and continuous stacking fault (SF) shearing. At 800°C a complex composite mechanism operates, involving deformation twinning, isolated SFs, and thermally activated dislocation climb. Notably, under low-stress conditions at 800°C, the formation of sessile Lomer–Cottrell (L–C) locks effectively pins subsequent dislocation glide, restricting the steady-state creep rate. Kinetic analyses validate this microscopic evolution, demonstrating a significant decrease in the apparent activation energy (from 515.3 kJ/mol to 446.2 kJ/mol) accompanied by an increase in the apparent stress exponent (n), signifying a macroscopic transition toward a dislocation-climb-controlled regime. Finally, while intergranular fracture remains the primary failure mode, creep damage is profoundly accelerated by sub-surface oxidation (≥750°C) and the stress-induced transgranular fragmentation or interfacial debonding of brittle primary MC carbides. These findings comprehensively elucidate the boundary conditions for mechanism transitions in GH4151, providing a critical theoretical foundation for the microstructural optimization and life prediction of advanced turbine disk alloys.