Effect of temperature and strain rate on the hot workability behaviour of Ni–25Cr–14W superalloy: An approach using processing map and constitutive equation

Abstract

The hot workability of Ni–25Cr–14W alloy is studied through isothermal hot compression tests in the temperature (T) range of 1000–1200 °C and in the strain rates(ε̇) of 0.001–10 s⁻¹ in a thermomechanical simulator. Flow stress data show stable flow curves at T > 1050 °C and ε̇ < 0.1 s⁻¹. The values of flow stress decrease with increase in T or decrease in ε̇. Based on processing map, safe region for hot workability has been identified in the temperature range of 1000–1200 °C and ε̇ of 0.001–0.1 s⁻¹ with maximum efficiency(η) of ~ 44% at 1175 °C and 0.001 s⁻¹. Dynamic recrystallization has been identified as the softening mechanism operating in the material at high temperature and lower ε̇. Incomplete recrystallization of the microstructures was noted during multi-step forging by varying T or ε̇, indicating the importance of maintaining the same during industrial processing.

Graphical abstract