Effect of cooling method after solution treatment on heat-treated microstructure and mechanical properties of a novel hard-deform Ni-base superalloy

It is investigated that the effect of solid-solution cooling methods on the heat-treated microstructure and resultant mechanical properties of a novel Ni-based wrought superalloy with a high content of（～55%,wt.） of γ’phase. The obtained microstructure after sub-solvus static recrystallization is uniform and fine with 10～30μm.The solid-solution cooling method has a significant impact on the recrystallized grain boundary and the distribution and size of γ’precipitates. As the solid-solution cooling rate decreases（water cooling ＞ oil cooling ＞ air cooling）,the sizes of primary and secondary γ’precipitates increase, while the number of tertiary γ’precipitates decreases.The tensile strengths at room temperature and 850℃ are closely related to the distribution of γ’precipitates, and the smaller the size of secondary γ’precipitates, the higher the tensile strength. Both the tensile plasticity at 850℃ and the stress-rupture property under 850℃/350MPa are largely determined by the recrystallized grain boundary（and the grain size）. The intergranular plastic fracture modes can be obtained after tensile and stress-rupture experiments at 850℃ with the presence of primary γ’precipitates and carbides on grain boundaries.