OBSERVATION OF CO NANOPARTICLE DISPERSIONS IN WC NANOGRAINS IN WC-CO CERMETS CONSOLIDATED FROM CHEMICALLY SYNTHESIZED POWDERS

High resolution, and analytical electron microscopy has been used to a nalyze morphological features in consolidated specimens of nanostructu red tungsten carbide-cobalt cermet materials prepared from chemically synthesized nanostructured WC-Co powder. The investigation includes st udying materials produced by consolidation (i) above, and (ii) below t he eutectic temperature by thermo-mechanical working. In the case of l iquid phase sintered material, the study includes examining the influe nce of a vanadium carbide additive on morphological features, as well as its effect in inhibiting grain growth. Electron microscope examinat ion of all consolidated materials reveals a dispersion of nanoprecipit ates within the WC nanograins of the WC-Co cermet. Micro-diffraction a nd analytical studies show that these nanoprecipitates are f.c.c. coba lt. This novel discovery is consistent with the concept that the nanop recipitates nucleate from cobalt retained within the WC nanograins, wh ich is a consequence of the intimate intermixing of tungsten and cobal t in the original chemical synthesis process.