Effect of Re Content on Solidification Structure of Fourth Generation Nickel-Based Single Crystal Superalloy

Based on the fourth generation nickel-based single crystal superalloy DD15, single crystal superalloys were prepared by adjusting its Re content (mass fraction) to 5%, 6% and 7%, respectively. The effects of Re content on the solidification microstructure characteristic and element distribution of the alloy were studied. The results show that with increasing Re content, the precipitation temperature and dissolution temperature of γ' phase of the alloy increased, while the solidus temperature decreased slightly and the liquidus temperature had no obvious change. With increasing Re content, both the primary and secondary dendrite spacings increased, the content of (γSymbolk@@γ') eutectic microstructure increased, while the size and volume fraction of γ' phase decreased. Increase in Re content could decrease the segregation degree of negative segregation elements such as Re, W, Mo, Cr and Co in the alloy structure, but increase the segregation degree of the positive segregation element Ta.