Unexpected Precipitation of a Re-Rich Phase in Single Crystal Superalloy CMSX-4 during Thermal Exposure

A Re-rich phase (up to 85.40% wt.Re) was occasionally found in a single crystal superalloy during thermal exposure. Interestingly, this phase is located in front of the dendrite periphery in the interdendritic region, while the Re is segregated in the dendrite core. Formation of this phase was suggested to relate to the unusual accumulation of the Re resulting from the uneven diffusion process of Re. Appearance of this phase may imply the preference of forming Re-Re atomic bond in the superalloys.