Microstructure and properties of in situ La2O3 and SiC co-doped WC-10 wt%Ni cemented carbides prepared by microwave sintering

Abstract In this work, composite powders of in situ La2O3 and 0.5 wt% SiC co-doped WC-10 wt% Ni cemented carbides were prepared by ball milling in conjunction with a surfactant-assisted hydrothermal method. The composite powders were compacted and then microwave sintered at 1450 °C, 1475 °C and 1500 °C. The composition, microstructure and mechanical properties of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical properties tests. The effects of the in situ La2O3 contents on the microstructure and mechanical properties of the fabricated samples were studied in detail. The results indicated that the addition of a small amount of La2O3 to the WC-10 wt% Ni cemented carbides enhanced the sintering, inhibited the WC grain growth, refined the WC grains and improved the mechanical properties. The average WC grain size decreased with an increasing amount of the added La2O3. For the La2O3 content of 0.5 wt%, the relative density, hardness, bending strength, and fracture toughness (KIC) of the WC-10 wt%Ni-0.5SiC-0.5La2O3 cemented carbides prepared at 1475 °C reached their maximum values of 99.75%, 1955 HV, 2114.3 MPa and 16.19 MPa⋅m1/2, respectively. It was also revealed that grain refinement, crack deflection, crack bridging and microcrack toughening were the strengthening and toughening mechanisms of the carbides. Additionally, the corrosion resistance of the WC-10 wt%Ni-0.5 wt%SiC-xLa2O3 cemented carbides in 3.5% NaCl aqueous solution was improved with in situ La2O3 doping and the best corrosion resistance was obtained for the WC-10Ni-0.5SiC-0.5La2O3 cemented carbides. The present results show that La2O3 and SiC co-doped WC-10 wt% Ni cemented carbides had excellent and comprehensive performances.