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Ti-doped WC-Ni3Al cemented carbide was prepared by spark plasma sintering for improving mechanical properties. The effect of different Ti contents on the microstructure and mechanical properties of WC-Ni3Al cemented carbide was investigated. The results show that due to Ti addition, the small amount of Al2O3reactively formed in WC-Ni3Al is smaller and more uniform than the sintered sample without adding Ti. The refinement of Al2O3 and the in-situ (Ti, W) C synergistically enhance the hardness of the WC-Ni3Al cemented carbide. Meanwhile, the fracture toughness is improved because the in-situ (Ti, W)C and WC have a better interface combination, facilitating the bridging and deflection formation of cracks. The WC-Ni3Al cemented carbide with 3% (mass fraction) Ti obtains the optimal mechanical properties, with hardness of (19.29±0.18) GPa and fracture toughness of (13.14±0.24) MPa·m1/2.

In order to reduce the sintering temperature and obtain higher fracture toughness of WC cemented carbides without metallic binder, WC cemented carbide was toughened by MgO and B2O3. Dense WC-MgO-B2O3 bulk materials were prepared at the relative low temperature of 1400℃ via spark plasma sintering(SPS), and the effects of MgO-B2O3 addition on sintering mechanism, microstructure evolution and mechanical properties of WC cemented carbides without metallic binder were studied. The results show that the addition of MgO-B2O3 promotes the sintering densification of WC, and reduces the sintering temperature of WC cemented carbides without metallic binder. With the increase of MgO-B2O3 contents, the morphology of some second phases in the microstructure is gradually transformed from short rod-shaped to long rod-shaped, and then to aggregated block. When MgO-B2O3 content reaches 8% (mass fraction), the bulk material has better fracture toughness of (9.45±0.37) MPa·m1/2, and its hardness is (18.16±0.17) GPa.

In this paper, WC-10Ni 3 Al cemented carbides were prepared by the powder metallurgy method, and the effects of ball-milling powders with two different organic solvents on the microstructure and mechanical properties of cemented carbides were studied. We show that the oxygen in the organic solvent can be absorbed into the mixed powders by ball-milling when ethanol (CH 3 CH 2 OH) is used as a ball-milling suspension. This oxygen leads to the formation of α-Al 2 O 3 during sintering, which improves the fracture toughness, due to crack deflection and bridging, while the formation of η-phase (Ni 3 W 3 C) inhibits the grain growth and increases the hardness. Alternatively, samples milled using cyclohexane (C 6 H 12 ) showed grain growth during processing, which led to a decrease in hardness. Therefore, the increase of oxygen content from using organic solvents during milling improves the properties of WC-Ni 3 Al composites. The growth of WC grains can be inhibited and the hardness can be improved without loss of toughness by self-generating α-Al 2 O 3 and η-phase (Ni 3 W 3 C).