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A new database for thermodynamic information for cemented carbides has been developed. A full description of the alloy system C-Co-N-Nb-Ta-Ti-W is presented. The work has involved both thermodynamic evaluations of lower order systems and experimental investigations. Full new assessments of the quaternary Ti-W-C-N, Ta-W-C-N, and Nb-W-C-N systems have been performed, including tests of the influence of model parameters on miscibility gaps in higher order systems. A new improved description of the Co-W-C system based on new experiments is used in the present work.The main results of the experimental work are • measurements of the composition of the cubic carbide in selected equilibria;• measurements of the temperatures of the liq ؉ fcc ؉ WC ؉ gr. and liq ؉ fcc ؉ WC ؉ M 6 C equilibria in the Co-W-C and Co-W-X-C (X ‫؍‬ Ti, Ta, Nb) systems; and • measurements of the solubility of Ti, Ta, and Nb in liquid in multicomponent alloys.The results of the assessments have been implemented into a new database. The database has successfully been used in a parallel project to simulate the formation of ␥-phase free zones in cemented carbides. A few other applications of industrial relevance are presented.over the entire composition range. An established method,

The thermodynamic properties of the Me-Co-C (Me ϭ Ti, Ta, or Nb) systems are of interest for cemented carbide applications. The model parameters for the Gibbs energy of the individual phases have been evaluated using the CALPHAD method. The reassessment of the Ti-Co-C system was based on the recent evaluations of the Ti-C and Ti-Co binary systems. The Ta-Co-C and Nb-Co-C systems have been reviewed and the thermodynamic properties have been evaluated. Due to the large scattering of the experimental data, DTA investigations of the eutectic temperature in the Co-MeC sections have been carried out in the present work and the results were used in the optimization. The importance of controlling the carbon activity during the experiments is emphasized. Various isothermal and vertical sections in the Me-Co-C systems and a projection of the liquidus surface of the Ti-Co-C are reported. Most of the experimental information is satisfactorily accounted for by the present thermodynamic description.