Fabrication and mechanical properties of WC-Al2O3 cemented carbide reinforced by CNTs

Carbon nanotubes (CNTs) reinforced WC-Al2O3 cemented carbides were prepared by hot pressing technique. The microstructure and components of composites were studied by Scanning Electron Microscope (SEM), Laser Raman spectroscopy and X-ray diffraction (XRD). The hardness and fracture toughness were analyzed by Vickers hardness tester. The experimental results showed that the WC-Al2O3-CNTs composite exhibited a significant increase in fracture toughness and Vickers hardness compared with WC-Al2O3 composite, which could be ascribed to evolution of microstructure resulted from the incorporation of CNTs. The minimum value of grain size was obtained in the WC-Al2O3-CNTs-0.5 cemented carbide and that sample possessed a better mechanical property compared with other WC-Al2O3 cemented carbides. The properties of the composite decreased sharply when the content of CNTs in WC-Al2O3 cemented carbide surpassed 1 wt %. The toughening and strengthening mechanisms of WC-Al2O3-CNTs cemented carbide including crack bridging, CNTs debonding, crack deflection and pull-out were studied respectively.