Solid solution extent of WC and TaC in Ti(C,N) as revealed by lattice parameter increase

Abstract

Materials development of cermets for cutting tools has come to a new stage where molybdenum is no longer indispensable. The key is the addition of a solid-solution treatment of hard phase powder mixtures before sintering with metallic binders. In this paper, ceramic powders of Ti(CN), TaC and WC are mixed, compacted and heat treated to form (Ti, W, Ta)(C,N) solid solutions at elevated temperatures. The influence of temperature and duration of the treatment on the solid solution extent is examined through measurement of the X-ray diffraction (XRD) spectra and the lattice constant. After treating at 1700°C for 1 h, the XRD spectra revealed the disappearance of the WC peaks. The lattice parameter of titanium carbonitride increased with increasing reaction time and temperature and stabilized after treating at 1700°C for 1·5 h. Cold isostatic pressing (CIP) at 350 MPa following uniaxial pressing at 180 MPa did not seem to have too much added influence on the solid solution extent, but CIP ed samples did give less scattered data. © 1994.