Synthesis and Characterization of WC-6Co Nanocrystalline Composite Powder

WC-6Co nanocrystalline composite powders without excess C and decarburization phases were synthesized via a facile route including spraying conversion, calcination and in situ reduction-carbonization processes. The phase constituents obtained by XRD show that the as-prepared powders after each step of the preparation are amorphous, WO₃ and Co₃O₄ phases, WC and Co phases, respectively. Pure WC-Co composite powders could be obtained by a reduction-carbonization process heat treated at 900 °C for 1 h under a hydrogen atmosphere due to the catalytic effect of Co on the carbonation reaction. The effects of heat treatment temperature on phase constituents of powders were investigated in a range of 700∼900 °C. Morphology and microstructure of powders were observed by SEM and HRTEM. The results indicate that the morphology of powder is spherical. The grain size of WC is about 0.36 μm, and the crystalline size of WC is about 56 nm, which indicates that the WC grain is polycrystalline and composed of many crystallites. It is also found that the individual particles of WC are bonded together under the action of Co. Furthermore, a few sintering necks could be observed in the composite powders due to the contacts between WC particles. The stoichiometry of WC-Co composite powders could be adjusted easily. Moreover, the formation process and mechanism of the sphere structure were also discussed in this paper.