Mechanical properties and cutting tool performance of ultrafine grain cermet

Abstract

Formation of solid solution (Ti, W) (C, N) in ultrafine grain TiCN base cermets has been studied. The solid solution realised high hardness of cermets. The formation of the W-rich solid solution had been found to be affected by sintering conditions, such as sintering temperature, N2 gas pressure and the ratio N/(C + N) of starting powder. The sintering conditions were considered to introduce some denitrification, which accelerates precipitation and growth of the W-rich solid solution phase around TiCN core structures. Further effect of WC content on the ultra fine grain TiCN cermets has been studied besides the solid solution formation around TiCN core. Effect of WC content on mechanical properties has been studied, varying grain size of TiCN, amount of WC and Co/Ni contents. We have confirmed that WC was solved also into Co/Ni metallic binder phase, which improved fracture resistance, especially at elevated temperature. This improvement kept wear resistance as high as well, and realised the cermets of high mechanical properties for cutting tools of high performance.