Microstructure evolution, hot deformation behaviour and processing map of Inconel X-750 superalloy in sub-solvus and super-solvus temperature ranges

Abstract

Hot deformation behaviour of Inconel X-750 superalloy was investigated using the hot compression test in the temperature range of 950–1150 °C and strain rate of 0.001–1 s−1. After excluding the effect of friction and adiabatic heating from obtained flow curves, three constitutive equations and processing maps were developed. The hyperbolic sine with an activation energy of 461 kJ. mol−1 could confidently predict the flow stress pattern of the alloy with a correlation coefficient (R) of 0.99 for both sub and super-solvus temperatures. The processing map also accurately depicts two domains with high values of power efficiency η greater than 34%. Among these, the temperature range of 1090–1150 °C and strain rates between 0.01–0.1 s−1 are optimum and safe to obtain a fully dynamically recrystallized (DRXed) structure. The microstructure of the other domain with a high η value has not depicted a recrystallized structure and the high-power efficiency value was associated with dynamic precipitation of gamma prime (γ′) at temperatures within the range of 980–1100 °C and strain rates lower than 0.01 s−1. Finally, the correlation between processing maps, flow curves and microstructural observations was analyzed authoritatively. The MC precipitation takes deformation into trouble in the temperature range of 1050–1100 °C and strain rates higher than 0.01 s−1 due to Zener drag pining effect.

Keywords

• Superalloy
• Quantitative equations
• Dynamic precipitation
• Gamma prime
• Processing maps
• Flow instability