An experimental study of the precipitation kinetics of pre-rolled Ni-Span-C 902 superalloy

Abstract In the present work, the effects of cold work and aging parameters on the microstructure and precipitation kinetics of Ni-Span-C 902 superalloy were studied. The solution treated alloy was cold-rolled to different deformations from 30 to 60% followed by aging in the temperature range of 450–850°C for different times, from 102 to 105 seconds. The results showed that the 50% cold-rolled alloy attained its maximum hardness by aging at 650°C for 105 seconds. This was concurrent with the fine distributed gamma′ precipitates that appeared in the microstructure. By increasing temperature from 750 to 850°C, overaging occurred due to the increase in gamma′ particle size and the formation of epsilon-phase. The estimated activation energy of the precipitation reaction, based on Johnson–Mehl–Avrami–Kolmogorov analysis, was determined to be 254 kJ · mol−1 for the 50% cold-rolled alloy.