An investigation on the hot deformation behavior and processing maps of Co-Ni-Cr-W-based superalloy

Abstract

The hot deformation behavior of Co-Ni-Cr-W-based superalloy was investigated by means of hot compression tests at the temperature range of 1000–1200 °C with strain rate range of 0.01–10 s−1. Processing maps were developed on the basis of experimental data and the employing principles of the dynamic materials model (DMM). The hot deformation activation energy is calculated about 522.37 kJ/mol. At strain above 0.1, the maps present two domains. Microstructural observations revealed that the partial dynamic recrystallization (DRX) occurred in the domain I (at 1025–1115 °C and 0.01–0.03 s−1), and the full DRX occurred in the domain II (at 1120–1180 °C and 0.08–0.8 s−1) at strain of 0.7. The domain II in the processing maps corresponding to different strains revealed the different microstructural evolution mechanism. The domain at strain 0.3 represents work hardened and partial DRX or/and DRV. That at strain of 0.5 is mainly related with DRV and DRX. The fraction of Σ3 twins was increased with the increasing of strain. The Σ3 twins help to lead to the grain refinement and homogenization during the hot deformation. On the basis of the analysis of the processing maps and microstructure evolution, the optimum hot working conditions were determined to be 1120–1180 °C, 0.08–0.8 s−1 and the strain above 0.5.