Effect of pre-alloyed raw materials on the microstructure of a (Ti,W)(C,N)-Co cermet

Four alloys manufactured from different combinations of powders (TiC + TiN + WC; Ti(C,N) + WC; (Ti,W)C + TiN and (Ti,W(C,N)) were studied using X-ray diffractometry, optical microscopy (OM), scanning electron microscopy (SEM) and analytical electron microscopy (AEM). The alloy manufactured from binary powders had a smaller grain size and a more inhomogeneous microstructure than the other alloys. The alloys manufactured with WC contained an inner rim around Ti(C,N) cores, as well as W-rich cores. Thermodynamic calculations suggest that these are formed during solid-state sintering at 900 degreesC in a low nitrogen activity. The outer rim had a composition that is in good agreement with calculations of the equilibrium during liquid phase sintering at 1450 degreesC. (C) 2001 Published by Elsevier Science Ltd.