Ultrafine WC-0.5Co-xTaC cemented carbides prepared by spark plasma sintering

Ultrafine (below 500 nm) tungsten carbide (WC) - 0.5 wt% cobalt (Co) cemented carbides were prepared by spark plasma sintering (SPS), containing varied tantalum carbide (TaC) contents, at 1500 degrees C under 50 MPa. The sintering behavior and microstructure of these materials were investigated. It was found that adding TaC could get a rapid shrinkage period during sintering and make a finer microstructure with a more narrowing range of the grain-size distribution. Adding inadequate or excessive amount of TaC, however, not only lower the sinterability but also get a result against the finer microstructure. Moreover, the (Ta,W)C solid-solution phase (formed by the part dissolution of WC in TaC grains) was mainly gathered at the WC grain boundary, and Co film was found. Benefiting from the ultrafine and homogeneous microstructure, these materials maintained excellent hardness and improved fracture toughness.