The Microstructure Stability of Precipitation Strengthened Medium to High Entropy Superalloys

Medium and high entropy superalloys based on the Ni-Co-Fe system with strengthening L1 2 γ′ precipitates have been developed. The present study has shown that by controlling the elemental partitioning between γ/γ′, thermal stability of γ′ can be enhanced in the high entropy γ matrix. Most importantly, high entropy superalloys exhibit stable γ–γ′ microstructures with no TCP phases after long-term exposure at elevated temperatures. Therefore, a new alloy design space for stable γ–γ′ microstructure has been presented. Furthermore, due to relatively high content of Fe and Ti, their raw materials cost and alloy density can potentially be lower than those of conventional superalloys.