Thermodynamic Description of Ternary Fe-B-X Systems. Part 7: Fe-B-C

Thermodynamic description of the Fe-B-C system in its iron-rich corner is developed in the context of a new Fe-B-X (X = Cr, Ni, Mn, Si, Ti, V, C) database. The thermodynamic parameters of the binary sub-systems, Fe-B, Fe-C and B-C, are taken from earlier assessments modifying the B-C description. The parameters of the Fe-B-C system are optimized in this study using experimental thermodynamic and phase equilibrium data from the literature. Liquid, beta-rhombo-B and graphite phases are described using the substitutional solution model, while the ferrite (bcc), the austenite (fcc), the cementite (M3C) and the M23C6 phases are described with the sublattice model and the borides, Fe2B, FeB and B4C, are treated as stoichiometric phases. A good correlation was obtained between the calculated and the experimental thermodynamic and phase equilibrium data. The description is recommended to be used at the composition region of wt% C + wt% B < 15 and at temperatures below 2700°C