Effect of ultra-fine powders on the microstructure of Ti(CN)–xWC–Ni cermets Original Research Article

Microstructural and compositional analyses of Ti(CN)–xWC–20Ni cermets were done in order to better understand the dissolution behavior of ultra-fine sized Ti(CN) and WC in comparison with a micro-sized system. The WC content was varied from 5 to 75 wt%. A discrete composition (∼50 wt%WC addition) at which WC does not dissolve any longer in the ultra-fine system was found. At this composition, the W concentrations, not only in the rim, (Ti,W)(CN), but in the binder as well were at a maximum. Depending on the powder size and morphology, these values are strongly affected due to the surface areas of Ti(CN) and WC for dissolution and precipitation sites. Furthermore, a significant improvement in the mechanical properties of simple ultra-fine systems was found, compared to that of corresponding micron-sized systems (Hv 14–15 GPa, KIC 8–10 MPa m1/2), which are comparable to commercial cermets. The refined microstructure and high fraction of rim phase in the ultra fine systems are likely responsible for this difference.