Synthesis and characterization of ultrafine WC-Co by freeze-drying and spark plasma sintering

A new process for the production of ultrafine WC-Co cemented carbide was developed by freeze-drying and spark plasma sintering. Ammonium meta-tungstate was mixed with cobalt nitrate in the preliminary liquid solution, using liquid nitrogen as the cryogenic medium. W-Co composite nanopowder in the size range 20-30 nm was obtained after freeze-drying, thermal decomposition and reduction. WC-10%Co cemented carbide was synthesized by spark plasma sintering. The sintered body approached its theoretical density, and the crystal size was about 0.7 mu m, with hardness of 1719.3 HV0.5. When the sintering temperature increases, the hardness of the cemented carbide will decrease because of the growth in grain size. (C) 2008 Elsevier Ltd. All rights reserved.