Thermodynamic Assessment of the Co-Cr-Nb System

In this work, the Co-Cr-Nb ternary system was evaluated using the CALPHAD technique based on the experimental measurements of the isothermal sections at 1000, 1100 and 1200 °C. The solution phases including Liquid, Bcc, Fcc and Hcp were described by a substitutional solution model. The Laves phases were described by a two-sublattice model. The σ phase was described by a three-sublattice model of (Co,Nb) 8 Cr 4 (Co,Cr,Nb) 18 and the μ phase was described by a four-sublattice model of Co 1( Co,Cr,Nb) 2 (Nb) 4 (Co,Cr,Nb) 6 . The Co 7 Nb 2 was treated as a stoichiometric compound. A set of self-consistent thermodynamic parameters for the Gibbs energies of individual phase in the Co-Cr-Nb system has been obtained which leads to a great fit between calculated results and experimented data. The calculated liquidus projection and reaction scheme of the Co-Cr-Nb ternary system have also been presented.