A Reassessment of Ti-C-N based on a Critical Review of Available Assessments of Ti-N and Ti-C

The Ti-C system has been thermodynamically reassessed due to difficulties in the thermodynamic assessment of the Ti-Al-C system indicating that the stability of the TiC should be decreased. The new optimization of the Ti-C system made the fcc (δ) phase less stable, especially below 1800 K. The ternary Ti-C-N system was also reassessed based on an existing description of the Ti-N system and the new one for the Ti-C system. Information on the equilibrium between titanium carbonitride of various compositions and liquid Fe was used in order to estimate the interaction energy between C and N in fcc (δ) in the Ti-C-N system. The new assessment of the Ti-C-N system is thus consistent with a new assessment of the solubilities of titanium carbonitride in the various Fe phases. To fit the experimental information new values for the interaction parameters in liquid, α and δ phase were determined. Phase diagrams calculated using the new assessment are presented.