Thermodynamic assessment of the Ni-Co-M1 (M1 = Re, Ru) and Ni-Re-M2 (M2 = W, Ta) superalloy systems over the whole composition

Abstract

The phase equilibria of the Ni-Co-M1 (M1 = Re, Ru) and Ni-Re-M2 (M2 = W, Ta) ternary systems were thermodynamically assessed by the CALPHAD (CALculation of PHAse Diagrams) method based on the thermodynamic descriptions of the constitutive binary systems and experimental phase equilibria data available in the literature. The solution phases, i.e., fcc(Co, Ni), hcp(Co, Re, Ru) and bcc(Co, W, Ta), were described using substitutional solution model and the binary phases σ(ReW), χ(Re3W), χ(Re3Ta), NiTa2, μ(NiTa), Ni2Ta and Ni3Ta with the solubilities of the third element were modeled by the sublattice models. A set of self-consistent thermodynamic parameters for each ternary system was finally obtained. Some representative isothermal sections and liquidus projections were calculated. Comparisons between the calculated results and experimental data show that almost all the reliable experimental data were satisfactorily reproduced by the present modeling.