Andreas Markström

Effect of Cr and V on phase equilibria in Co–WC based hardmetals

Abstract New measurements of the influence of Cr and V on the melting temperature of the binder phase in Co-based hardmetals are presented. It was shown that both Cr and V affect the melting temperature significantly. Cr decreases the melting temperature by over 100°C, and V by approximately 40°C. This is due to the high solubility of Cr and V in liquid Co, and this solubility was determined by experiments and calculations. The solubility of Cr in solid fcc-Co is also discussed, as well as the composition of the MC, M7C3 and the M6C carbides in alloys with Cr and V. The new experimental information is used to obtain a reliable thermodynamic description of the binder phase (Co-rich) in C – Co – Cr – W and C – Co – V – W alloys. Calculated equilibria are compared with experiments.

Experimental and thermodynamic evaluation of the Co-Cr-C system

Abstract New experimental results on the liquid+graphite+M7C3 equilibrium are presented. The solubility of Co in the M7C3 carbide has been measured at 1523 and 1723K. These measurements together with recently published measurements on the fcc+graphite+M7C3 equilibrium show that the solubility of Co in the M7C3 is much higher than predicted from thermodynamic calculations. A new thermodynamic description of the Co–Cr–C system is presented which accurately describes the solubility of Co in the M7C3 carbide in the temperature range 1373–1723K.