Evolution of the microstructure and microhardness of a new wrought Ni-Fe based superalloy during high temperature aging

The changes of the microstructure and microhardness of a new wrought Ni-Fe based superalloy with γ/γ′ two-phase structure were investigated during high temperature aging at 750 °C up to 3000 h. It was found that γ′ particles grew into large ones with spherical morphology and the growth rate was consistent with the LSW model. No other detrimental phases were observed besides small blocky type Cr-rich M23C6 carbides existed around grain boundaries. In addition, the microhardness of aged Ni-Fe alloy decreased about 13% in the first 500 h aging and then dropped about 21% after aging for 3000 h. The microstructural evolution during high temperature aging was characterized in terms of γ′ particles morphology, size and growth kinetics, and were further correlated with the changes of its microhardness.