The Effect of Long-Term Aging on the Microstructure and Properties of a Novel Nickel-Based Powder Superalloy FGH4113A

This study investigates the microstructural evolution and its effect on the fatigue performance of a novel nickel-based powder superalloy FGH4113A (WZ-A3) after long-term aging at 760 °C and 815 °C. The results show that long-term aging both at 760 °C and 815 °C has no significant effect on the grain size and morphology of the alloy. After aging at 760 °C for up to 2020 h, the size of the γ' phase remains unchanged, and its morphology transitions from nearly square to nearly spherical. During long-term aging at 815 °C for 440 h, γ' phase coarsening and spheroidizing occur simultaneously. With prolonged aging time, the size and spheroidization degree of the γ' phase further increase. During long-term aging up to 440 h at 760 °C, the dispersed granular MC and M₆C carbides dissolve and re-precipitate. By 2020 h of aging, flocculent carbides precipitate and non-continuous M₆C and M₂₃C₆ accumulate at grain boundaries. After long-term aging at 815 °C for 440 h, flocculent carbides begin to precipitate within the grains. By 2020 h of aging, a large amount of flocculent carbides precipitate with significant coarsening and enrichment of the grain boundary carbides. Due to the insignificant coarsening of the γ' phase as well as the enrichment and precipitation of the grain boundary carbides, the fatigue performance of the alloy decreases slightly after long-term aging.