Thermodynamic assessment of the Co–Cr–Ni, Co–Cr–W and Co–Ni–W

Abstract

The thermodynamic description of the Co–Cr–Ni, Co–Cr–W and Co–Ni–W systems is the basis of material design for Co-WC cutting tools and superalloys. A common feature of the three ternary systems is that the detrimental topologically close packed (TCP) phases (μ and σ phases) have large ternary extensions, which makes it crucial to provide a reliable description of the TCP phase boundaries. In order to obtain an accurate description of the TCP phase boundary, the effect of magnetism on the Gibbs energy of the TCP phases containing ferromagnetic elements must be considered. In the present work, the effect of magnetism on the Gibbs energy for the Ni-related TCP phases has been discussed. The magnetic related parameters TcNiσ, βNiσ, GoNidis_σ, TcNiμ, βNiμ, GoNidis_μ were evaluated. CALPHAD (CALculation of PHAse Diagrams) assessment for the ternary systems has been performed. The present CALPHAD description can well describe the experimental data.