Microstructural evolution and deformation behavior of a Fe-Ni base superalloy during aging

GH2984 alloy is a Ni3Al (γ′) particle strengthened by Fe-Ni-base alloy with a promise to be used in boiler tubes in the next generation power plants. A primary concern over this material is its alloy property degradation during long-term service in the designed environment. This work investigates the microstructural evolution of the alloy during aging and the impact of the evolution on deformation behavior of the alloy. The results show that the γ′ uniform precipitation during short-term aging (8 h) at 750 °C provides a superior alloy strength. Nevertheless, the γ′ coarsens obviously during long-term aging (5400 h), and the Orowan strengthening effect decreases significantly as the particles spacing increases. On the other hand, large γ′ particles increase the ductility of the grain boundary, and thus inhibits the crack nucleation during alloy deformation. However, the effect of large γ′ particles on the strength of grain boundary is relatively small.