The application of thermochemical data to the production of tungsten, tungsten carbide and tungsten-copper powders

The results of studies of the effects of temperature and H2/H2O ratio on the morphology of tungsten powder produced from WO3 are discussed in relation to the W-O phase diagram and the stabilities of the suboxides W20O58, W18O49 and WO2. The results of these studies are combined with predictions based on the 'predominance area' diagram for the W-C-O system and used to demonstrate how the particle morphologies of WC may be controlled during the direct carburisation/reduction of WO3 with carbon monoxide. The possible reduction behaviours of metal tungstates are outlined and a controlled reduction technique is described for the production of tungsten-copper composite powders for the manufacture of electrical contacts. (author)