Precipitation and thermal instability of M23C6 carbide in cast Ni-base superalloy K452

During long-term thermal exposure M23C6 dendritically precipitates from the supersaturated γ matrix and then changes in shape from flower-like dendrite to irregular block to regular polyhedron. The reduction in the interfacial energy is responsible for the morphological transition, but the stable morphology of the carbide is principally determined by the anisotropy of the interfacial energy between the carbide and the γ' in the M23C6-γ' cell. In addition, M23C6 has a negligible influence on the tensile property of the thermally exposed alloy even though it can block the mobile dislocations and stacking faults to some extent.