Preparation of WC/MgO composite nanopowders by high-energy reactive ball milling and their plasma-activated sintering

Nanosized WC/MgO powders are synthesized by high-energy ball milling the mixture of WO3, C, and Mg elements in an atomic ratio of 1:1:3 under argon gas atmosphere at room temperature, and the composite is made by plasma-activated sintering. The microstructure of the mixture powders produced by ball milling and the sample consolidated by plasma-activated sintering is investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It is indicated that self-propagating reduction reactions occur between the mixed element powders during high-energy ball milling, leading to the formation of nanosized WC/MgO crystalline particles with an average size of 35 nm after ball milling for 5h. The obtained nanosized WC/MgO powders are consolidated by plasma-activated sintering at 1473K under the pressure in a range of 5 to 7.5 kN for 1.05 ksec, and then WC/MgO composite with nanomicrostructure and full density can be obtained. The WC/MgO composite exhibits high hardness and high fracture toughness in comparison with commercial WC/Co composites.