Ultrafine hardmetals prepared by WC–10 wt.%Co composite powder

Ultrafine tungsten carbide–cobalt (WC–10 wt.%Co) composite powder was synthesized via spray-drying and direct reduction and carburization process in vacuum, which includes precursor preparation by spray-drying of a suspension of ammonium metatungstate (AMT) and cobalt carbonate (CoCO3), calcination to evaporate volatile components, formation of tungsten–cobalt mixed oxide powder (CoWO4/WO3), ball-milling with carbon black, and subsequent direct reduction and carburization reaction in vacuum. The synthesis temperature of WC–10 wt.%Co composite powder without η or graphite phases is lower than 1000 °C. The calculated particle size by BET test is 0.29 μm. Coarse WC powder (FSSS: 0.9 μm) and Co powder (FSSS: 1.0 μm) (WC:Co = 9:1 in mass) were added into the obtained WC–10 wt.%Co composite powder with addition of 30 wt.%, 50 wt.% and 70 wt.%, respectively. Results show that the hardmetal fabricated from 70 wt.% (WC–10 wt.%Co composite powder) + 30 wt.% (90 wt.%WC + 10 wt.%Co coarse powder) mixed powders exhibits a fine microstructure as well as optimum mechanical properties.