Stability of N in Ti(CN) Solid Solutions for Cermet Applications

Abstract

In recent years the demand for Ti(CN) based cutting tool materials has increased significantly. The presence of N in a TiC lattice of B1 (NaCl) structure improves the cutting performance of the tool materials by refining the microstructure and toughening the system. However, it is known that N in Ti(CN) is unstable and this causes difficulties in the manufacture of tools as well as in the control of final compositions. This instability of N is often explained with reference to the ideal mixing behaviour of TiC and TiN. In this study the dissociation of N from Ti(CN) of various C:N ratios was carefully measured. It was found that the loss of C and N was influenced very little by the initial C:N ratio. This indicates that the affinity of N for Ti is as strong as that of C in Ti(CN), making the system relatively stable at high temperatures. The results are discussed in the light of other experimental data. PM/0725