A study on microstructural changes in Ti(CN)–NbC–Ni cermets

The demand for Ti(CN)-based cutting tool materials has grown steadily over the past years. The presence of nitrogen in a TiC system improves the cutting performance of the tool materials by refining the microstructure and toughening the system. Furthermore, the addition of various carbides tunes the performance of cermet tools significantly for purposes of metal cutting. This paper reports an investigation of the effect of added NbC on the microstructure of a Ti(CN)–Ni system. The amount of NbC added varied from 5 to 40 wt.% and the nitrogen content of the Ti(C1−xNx) varied from 0 to 1. The result showed that a (Ti, Nb)(CN) solid solution formed around the Ti(CN) particles in the presence of low levels of NbC. At high NbC content (>10 wt.%) the solid solution tended to form a rim structure around the NbC. The nitrogen content of the Ti(CN) strongly influenced the general sizes of the particles in the final microstructure. The major factors which control these changes were investigated and the relationship between stability and nitrogen content are discussed.