WC-Co composite made with doped binder: The effect of binder proportion on microstructure and mechanical properties

Apart from hardness and density, the durability of cutting tools and other wear parts made of WC-Co composites depends on the homogeneity of the material. A homogeneous composite powder is obtained by mixing the carbide and the binder for long periods. To shorten the homogenization time and improve the sustainability of these products, a new type of binder was created by incorporating the grain growth inhibitor into the cobalt binder. The presence of the inhibitor in the binder is supposed to improve the latter's distribution in the mixture and make the binder harder, therefore more easily incorporable into the mass of the tungsten carbide particles, reducing the homogenization time. A WC powder with a particle size of about 0.5 μm was mixed with 6, 9 and 12% by weight of cobalt powder doped with Cr3C2 (doped binder). Classic mixtures (WC + Co + Cr3C2) were also prepared to assess the effect of the doped binder. The mixtures were prepared by planetary ball milling for 10 h, with a speed of 600 rpm, using a balls/powder ratio of 4: 1, and 20 ml of ethanol as an anti-caking agent. Samples were shaped and sintered by SPS technique at 1150 °C with a heating rate of 50 °C/min and a pressure of 50 MPa. As expected, a more homogenous microstructure is obtained in the samples made with the doped binder. The composites with 6 and 9 wt% Co has superior densification thanks to the doped binder. The best hardness/toughness compromise is registered for composites with 9% Co (2100 HV30 and 9.1 MPa*m1/2). Increasing the cobalt content to 12% decreases the hardness but does not improve toughness (9.5 MPa*m1/2).