Fabrication and properties of hot-pressing sintered WC-Al2O3 composites reinforced by graphene platelets

To enhance the toughness of the WC-Al2O3 composite, graphene platelets (GPLs) were incorporated to this ceramic composite by using ball milling and hot pressing sintering. The influences of graphene on microstructure and mechanical properties of the WC-Al2O3 composites were investigated. Results of the experiments showed that the grain size of the composite first diminished and then increased gradually along with the increase of graphene content. Both the Vickers hardness and toughness increased first and then diminished along with the increase of graphene content. The optimized composite exhibited the highest Vickers hardness (18.78 GPa) and the highest fracture toughness (11.09 MPa.m(1/2)) at the indentation load of 294 N (30 kg) when incorporated with 0.3 wt% GPLs, which are about 18.7% and 40.8% higher than that of WC-Al2O3 without GPLs, respectively. However, the relative density of the WC-Al2O3 composites decreased stably along with the increase of graphene content. Agglomeration of GPLs and porosity were observed in the composites with high content, which weakened the properties. The toughening mechanisms are proposed to be crack deflection, crack bridging, graphene pull out and grain refinement.