Predictive approach to thermodynamic properties of the metastable Cr3C carbide

In thermodynamic modelling of phase diagrams it is often necessary to deal with the properties of metastable compounds, which are not known from experiments. As an illustrative example, the Cr3C(oP16) carbide is chosen, which is involved in the modelling of the Me3C(oP16) ('cementite') structure of the Fe-Cr-C system, but is metastable in the Cr-C system. The estimation of its thermodynamic properties, relying on regularities in bonding properties of 3d-transition metal carbides and an account of the vibrational entropy through the so-called 'entropy Debye temperature', are discussed in detail. The predictions are compared with values derived in thermodynamic modelling of the Fe-Cr-C phase diagram. Relying on the present results, calculations of metastable phase-equilibria in the Cr-C system are calculated and these were used in analysing information about Cr3C from splat-quenching experiments. (Author)