Hot deformation behavior and processing maps of iron-nickel based superalloy

Hot deformation behavior of iron-nickel based superalloy (multimet N-155) was investigated by hot compression tests, carried out in the deformation temperature of 850 °C–1150 °C with strain rates of 0.001–0.1 s−1. The results showed that during the hot deformation of the alloy, under the same temperature, the flow stress rises with the increase of strain rate. At the same strain rate, the flow stress decreases with the increase of the temperature. The constitutive equations of the alloy that describe the flow stress as a function of strain rate and deformation temperature were established and the calculated apparent activation energy was 584.996 Kj/mol. The results of metallographic analysis showed that the amount of dynamic recrystallization in the peak efficiency domain is higher than the other domains. The results also showed that by increase of deformation temperature and/or decrease of strain rate, the volume fraction of dynamic recrystallization increases. Processing maps under different strains were constructed for evaluation of flow instability regime and optimization of processing parameters. The optimum hot working window for alloy was obtained at the temperature range of 925 °C–1050 °C and strain rate of 0.001–0.003 s−1, with peak efficiency of 28 %. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim