Solidification path and phase equilibria in the liquid-solid range of cobalt-base alloy

For stellite 6 type alloys (Co-Cr-C-W), phase equilibria may be determined by several experimental methods, between liquidus and solidus temperatures. According to the composition of the different phases in this temperature range, two steps are found for the solidification path: from 1360 to 1280° C, a f c c solid solution based on Co-Cr crystallizes from the liquid phase; then, between 1280° C and the solidus temperature, the liquid phase meets and follows an eutectic line; at the same time, a eutectic precipitation of γ-phase and M₇C₃ takes place. Owing to the lack of diffusion of W in the solid phases, undercooling is observed at normal solidification rates.