CALPHAD study of cubic carbide systems with Cr

Sammanfattning: Cubic carbides (titanium, tantalum, niobium, and zirconium carbides) can constitute a significant proportion of so-called cubic and cermet grades, where it is added to substitute a portion of tungsten carbide. It is thus critical to understand and be able to thermodynamically model the cubic carbide systems. In order to do this, the thermodynamic descriptions of lower order systems, such as the Ti-Cr-C system, need to be well studied. To approach this goal, an extensive literature survey of thermodynamic data and phase diagram information on the Ti-Cr-C system, the Ta-Cr-C system, the Nb-Cr-C system and the Zr-Cr-C is presented in this work. Experiments are performed in the Ti-Cr-C system using powder metallurgy and heat treatments. The solubility of Cr in FCC_TiC phase was experimentally measured at 1773K and compared with previous studies showing that the solubility reported earlier is too large. Thereafter, a re-optimization of FCC_TiC and liquid interaction parameters of the Ti-Cr-C system was performed taking into account the experimental data obtained both from previous studies and this work. The Gibbs energy descriptions of the Cr-carbide end members were compared between the one from the in-house database [SandvikTDB] and from other studies. With the new description, the solubility of Cr in FCC_TiC is better described.