First-principles simulations of metal-ceramic interface adhesion: Co/WC versus Co/TiC

With the purpose to understand the fundamental difference between two industrially important classes of hard materials, WC-Co cemented carbides and TiC-Co cermets, we do a comparative study of Co/WC and Co/TiC interface adhesion. Using first-principles density-functional plane-wave pseudopotential calculations, we analyze the energetics and electronic structure of the Co/WC interface, and compare with previously reported results for Co/TiC. Values for the work of separation and the interface energy are provided for a set of model Co(001)/WC(001) interfaces with fcc Co and cubic WC, which is a relevant case in sintering of Ti(W)C-Co cermets. The known fact of better wetting for Co on WC than on TiC is confirmed and explained in terms of the electronic structure. Both Co/WC and Co/TiC are characterized by strong covalent Co-C interface bonds. The stronger adhesion in the Co/WC case originates from a larger contribution of the Co-W metal-metal bonding rather than from the Co-C bonds.