Hot Deformation Behavior, Constitutive Modeling and Processing Map of a Novel Nickel-Cobalt-Based Superalloy
Abstract
The hot deformation behavior of a novel Nickel-Cobalt-based superalloy for advanced aeroengine turbine disk applications was systematically investigated via isothermal compression tests (1090–1230 °C, 0.01–10 s−1) using a Gleeble-3800 simulator. Flow stress exhibits strong sensitivity to deformation temperature and strain rate, decreasing with rising temperature and decreasing strain rate. An Arrhenius-type hyperbolic-sine constitutive equation (ε = 0.5, R2 = 0.9890) incorporating the Zener–Hollomon parameter was established, yielding an activation energy of approximately 585 kJ/mol. A hot processing map was constructed based on the dynamic material model by superimposing power dissipation and plastic instability maps. Microstructure analysis shows that dynamic recrystallization (DRX) is the dominant softening mechanism, closely correlated with the power dissipation efficiency in the stable deformation domains, while instability regions are associated primarily with localized plastic flow. Combining the processing map with the microstructure observations, the optimum hot working window is identified at temperatures of 1180–1210 °C and strain rates of 2.7–10 s−1, where uniform fine equiaxed DRX grains are obtained. These results provide a quantitative basis for optimizing the industrial hot forming process of this superalloy.