Valence-electron structure and properties of main phases in Ti(C, N)-based cermets

Based on the empirical electron theory (EET) of solids and molecules, the valence-electron structures (VESs) of the main phases in Ti(C, N)-based cermets were calculated, and the relationship between the VES and properties was determined. The results indicated that the hardness of the phases with the same crystal structure could be compared using the covalent electron pairs, na, values on the strongest bonds and the plasticity by the sum of na values for the covalent bonds. The dissolution of N in TiC phase could improve the plasticity of TiC phase, and Mo, W and V dissolution could reduce its plasticity. However, Cr dissolution in the rim phase improved the plasticity of the rim phase, which should be advantageous for strengthening Ti(C, N)-based cermets. Based on those results, a Ti(C, N)-based cermet added with Cr3C2 was manufactured; the new cermet had more than twice the transverse rupture strength of a typical cermet.