Microstructure evolution and creep-rupture behaviour of a low-cost Fe-Ni-based superalloy

The pursuit of low-cost superalloys with excellent creep property is of great importance for practical engineering application. In this study, the creep performance, microstructure evolution and deformation mechanism of a low-cost Fe-Ni-based superalloy under the condition of 750°C/130 MPa and 700°C/200 MPa were investigated. The creep rupture life reached 14,715 h and 12,716 h, respectively, under the aforementioned conditions. After long-term creep, carbides and γ′ particles (Ni3(Al,Ti)) with spherical shape grew gradually due to the Ostwald ripening. Abnormal coarse needle-like γ′ phase presented at grain boundaries and grew along preferred orientation under the synergy effect of grain boundary migration, stress, and diffusion. Influence of precipitate-free zones, carbides, and coincidence site lattice (CSL) boundary on the creep properties were discussed. The creep deformation mechanism of the Fe-Ni-based superalloy were dominated by dislocations slip. Dislocations moved via by-passing the γ′ phase and formed dislocation bows around the precipitates.