Thermodynamic assessment of the Me-Co-C systems (Me = Ti, Ta, or Nb)

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2001-09, Vol.32 (9), p.2167-2174
• Main Authors: DUMITRESCU, Lucia F. S, EKROTH, Malin, JANSSON, B. O
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase diagrams of metals and alloys; Physics
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-001-0192-9

The thermodynamic properties of the Me-Co-C (Me = 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.