The influence of heat treatment and hot deformation conditions on γ′ precipitate dissolution of Nimonic 115 superalloy

摘要

In precipitation hardenable materials, it is desirable to determine the precipitate dissolution temperature for homogenizing the microstructure by controlling the size and distribution of the precipitates. In this research, the influence of various heat treatment and hot deformation conditions on the kinetics of γ′ dissolution and its morphological evolution in Nimonic 115 was studied. In addition, hot deformation behavior of the material was investigated using hot compression experiments at varying temperature (between 1,050°C and 1,175°C) and strain rates (between 0.01 and 1 s−1) up to a true strain of 0.8. The values obtained for the solvus temperature of γ′ precipitates by two methods are all in agreement indicating this temperature at approximately 1,165 ± 5°C. Through examination of the influence of temperature and strain rate on the hot deformation behavior, it was determined that the experimental flow stress observations could be effectively related to the processing parameters using an Arrhenius relationship. The results indicate that dynamic recrystallization is the main softening mechanism during the high temperature deformation of Nimonic 115, and it can be effectively promoted by increasing the deformation temperature. By deformation at temperatures higher than 1,125°C, a completely recrystallized microstructure is obtained.