Experimental investigation and thermodynamic calculation of the phase equilibria in the Co-Mo-W system

The isothermal sections in the Co-Mo-W ternary system at 600 °C, 800 °C, 1000 °C, 1100 °C, 1200 °C and 1300 °C have been determined using the Electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD) techniques. A thermodynamic assessment of the Co-Mo-W ternary system was carried out by the CALPHAD (Calculation of Phase Diagrams) method. The Gibbs free energies of the liquid and solution phases were described by the subregular solution models, and those of intermetallic compounds were described by the sublattice model. A consistent set of thermodynamic parameters has been derived for describing the Gibbs free energies of each solution phase and intermetallic compound in the Co-Mo-W ternary system. The calculated phase diagrams and thermodynamic properties in the Co-Mo-W ternary system are in good agreement with experimental data.