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 microst ructure and toughening the system. Furthermore, the addition of variou s carbides tunes the performance of cermet tools significantly for pur poses of metal cutting. This paper reports an investigation of the eff ect of added NbC on the microstructure of a Ti(CN)-Ni system. The amou nt of NbC added varied from 5 to 40 wt.% and the nitrogen content of t he 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 solutio n tended to form a rim structure around the NbC. The nitrogen content of the Ti(CN) strongly influenced the general sizes of the particles i n the final microstructure. The major factors which control these chan ges were investigated and the relationship between stability and nitro gen content are discussed. (C) 1998 Elsevier Science S.A. All rights r eserved.