Formation of Cuboidal Co₃AlC Precipitates in Carbon‐Containing Co–Al–W‐Based Superalloys

The influence of Carbon addition on a ternary Co–Al–W alloy is investigated especially regarding phase stability and partitioning behavior of alloying elements. During casting and subsequent cooling, C‐additon leads to the formation of an interdendritic carbide network and to the homogeneous precipitation of cuboidal E2₁ phase, Co₃AlC, in the W‐rich Co matrix. The solvus temperature of this phase is found to be about 1200 °C, which is significantly higher than the solvus temperature of the ternary L12 phase Co₃(Al,W). In the course of solution heat treatment, the Co₃AlC precipitates are dissolved and the carbides change in morphology and chemical composition. Further annealing leads to the precipitation of small cuboidal precipitates of L1₂ phase, Co₃(Al,W), and to a discontinuous precipitation of further phases.