The surface microstructure of TiC-(Ti,W)C-WC-Ni cermets sintered in a nitrogen atmosphere

The effects of nitrogen and a solid-solution carbide on the surface microstructure of TiC-(Ti,W)C-WC-Ni cermets were investigated. The binder enrichment layer with the cubic carbide was observed at the surface, the formation of which is attributed to the concentration gradient of nitrogen and constituent elements. This tendency is found to decrease as the dissolution rate increases when nano-sized TiC was employed. Coarsening behavior and the formation of a discrete layer were studied as a function of (Ti0.93W0.07)C carbide content and nitrogen pressure. The results were interpreted in terms of the relative thermodynamic stability of the carbide phases in the system.