Sintering behavior of ultrafine powders of WC and Mo₂C (particle size<1μ) obtained by CVD method was investigated under the atmospheres of hydrogen and vacuum with emphasis on the effects of particle size and atmosphere on their sinterabilities.
The sinterabilities of the WC and Mo₂C powders were higher in vacuum than in hydrogen. The fine WC powders gave the sintered bodies with the relative density of 100% by the sintering at -1700°C in vacuum. The relative densities of sintered bodies of the fine Mo2C powders reached 94-99% at 1500°C in vacuum. The sintered bodies of the fine carbide powders had fine-grain structures with the grain size of 0.5-2μ. The effect of atmosphere on the sintering of the carbide powders was interpreted on the basis of the different chemical behaviors of free carbon and surface oxide layer in hydrogen and in vacuum.