Effect of cobalt content on the microstructure and mechanical properties of coarse grained WC-Co cemented carbides fabricated from chemically coated composite powder

Coarse grained WC-Co cemented carbides with Co content varying from 3 wt% to 12 wt% were fabricated from composite powder. The composite powder was prepared through chemical coating method that cobalt encased on the surface of WC particles. Effect of Co content on microstructure of the WC-Co cemented carbide was investigated by XRD, SEM and TEM. The experimental results indicate that the nanostructured cobalt coating exhibits spherical shape with a particle size ranging from 200 to 400 nm, and the WC-Co composite powder represents unique feature of WC particle encased by cobalt. With increasing Co content from 3 wt% to 12 wt%, the gradual increase of WC grain size from 5.23 μm to 6.67 μm, fracture toughness from 24.66 MPa m1/2 to 28.83 MPa m1/2 and transverse rupture strength from 2367.05 MPa to 2849.22 MPa of the WC-Co cemented carbides were resulted. The enhanced overall performance was attributed mainly to the equilibrium shape of WC caused by the well-encasing of cobalt on WC grain. This may give insights on the application of other coarse grained WC-based cemented carbides fabricated by chemically coated composite powder.