Solidification behavior of Re‐ and Ru‐containing Ni‐based single‐crystal superalloys with thermal and metallographic analysis

To clarify the solidification behavior of Re‐ and Ru‐containing Ni‐based single‐crystal superalloys, four experimental alloys with varied contents of Re and Ru were investigated by differential scanning calorimetry (DSC) and metallographic techniques. To obtain the γ′‐solvus temperatures, the stepwise solution and aging heat treatments were used. DSC analysis shows that Re leads to the increase in freezing range and γ′‐solvus temperature. On the contrast, Ru only has negligible influence on the freezing range, but leads to the lower γ′‐solvus temperature. In comparison with Ru, Re leads to more severe segregation and higher eutectic fractions in as‐cast microstructures. Furthermore, the castability and phase stability of Ni‐based superalloys were analyzed by the results of DSC and metallographic analysis, such as freezing range, critical nucleation temperature, γ′‐solvus temperature and eutectic fractions. It shows that Re leads to the wider freezing range and lower critical nucleation temperature, indicating the worse castability of Re‐containing Ni‐based single‐crystal superalloys.