An experimental study of the sintering of nanocrystalline WC-Co powders

Since nanocrystalline WC-Co powder was produced over a decade ago, the sintering of nanocrystalline powders remains a technological challenge. The goal of sintering nanocrystalline powders is not only to achieve full densification but also to retain nanocrystalline grain sizes. This is difficult because of rapid grain growth at high temperatures. Previous studies on the sintering of nanocrystalline WC-Co have shown that grains grow rapidly during the early stage of sintering. But there are few studies on the mechanisms of grain growth and densification during this stage. This paper presents the results of an experimental investigation on grain growth and densification of nanocrystalline WC-Co powders during heat-up at equilibrium solid-state temperatures. The results have shown that nanocrystalline WC grains grow rapidly during this period concurrently with rapid densification. The rapid densification and grain growth are partially attributed to the surface energy anisotropy of tungsten carbide. The effects of vanadium carbide on grain growth at solid state during heat-up are also discussed.