High-Temperature Deformation Behavior of Superalloy XH43

With an aim to study the hot workability and establish the safe working zone for Ni-based superalloy XH43, cylindrical specimens were subjected to hot isothermal compression test at different temperatures (1173-1373 K) and strain rates (10⁻³-10 s⁻¹) using Gleeble thermo-mechanical simulator. Strain rate sensitivity and Zener–Hollomon parameter have been calculated. Processing maps and constitutive equations have been developed and verified with the experimental results. It is observed that dynamic recrystallization (DRX) is the principal flow softening mechanism. Strain rate sensitivity obtained through constant strain rate test (CSRT) m and through cyclic strain rate jump test (CSRJT) m’ is found to have close match initially up to 0.3 strain. Subsequently at higher strain m has marginal reduction, whereas m’ decreases drastically to low value. This is attributed to dynamic softening at higher strain, which is predominant in case of CSRJT where cyclic test is assisting the softening process. Activation energy Q obtained through CSRT is found to be slightly higher than activation energy (Q’) obtained through dynamic test like CSRJT and jump temperature test (JTT). This indicates less dragging force for deformation of alloy in dynamic tests, which is closer to industrial practice. It is also found that alloy has good workability in the temperature range of 1173-1373 K at strain rates of 0.01-0.001 s⁻¹. In this range of parameters, the alloy follows the constitutive equation very closely.