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In order to reduce the difficulty of preparing binder-less cemented carbide and further broaden its application prospects, tungsten carbide toughened by in situ elongated β-Sialon grains was developed via sintering ball-milled WC and α-Si 3 N 4 powders using Al 2 O 3 –ZrO 2 as a sintering aid and transformation additive. The two-step spark plasma sintering of the mixture at 1650 °C with dwelling at 1500 °C for 10 min was conducted under 30 MPa uniaxial pressure, and the densification behaviors, phase transformations, mechanical properties, and microstructures of the produced composites were investigated. The addition of Al 2 O 3 –ZrO 2 reduced the initial temperature of the densification process by approximately 100 °C and its final temperature by 200 °C (compared with the densification temperatures of pure WC and Si 3 N 4 materials) and fully transformed α-Si 3 N 4 to Sialon (Si–Al–O–N) phases. Microstructural characterization data showed that the WC matrix contained homogeneously distributed equiaxed and elongated β-Si 5 AlON 7 grains. The WC composites containing in situ elongated β-Sialon grains exhibited an optimal hardness of 18.93 ± 0.03 GPa and enhanced fracture toughness of 10.43 ± 0.27 MPa m1/2. The toughening mechanism of the β-Sialon phase involved the pull-out of elongated grains and crack bridging. [ABSTRACT FROM AUTHOR]

In this paper, WC-10Ni3Al 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 (CH3CH2OH) is used as a ball-milling suspension. This oxygen leads to the formation of α-Al2O3 during sintering, which improves the fracture toughness, due to crack deflection and bridging, while the formation of η-phase (Ni3W3C) inhibits the grain growth and increases the hardness. Alternatively, samples milled using cyclohexane (C6H12) 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-Ni3Al composites. The growth of WC grains can be inhibited and the hardness can be improved without loss of toughness by self-generating α-Al2O3 and η-phase (Ni3W3C). [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of WC-10 wt%Ni 3 Al cermets were examined after compression in the temperature range of 650–900 °C. Transmission electron microscope (TEM) analysis indicates that plastic accommodation during the deformation process is primarily due to deformation of both the WC and the Ni 3 Al binder. Yield loci slip mode analysis was used to confirm that dislocations, stacking faults, and even twins can exist on the prismatic plane {01 1 ‾ 0} in WC at high temperatures. The existence of stacking faults and twins make the material have obvious plastic deformation above 850 °C. In addition, the WC-10%Ni 3 Al sample exhibits high compressive strengths of ∼1300–1650 MPa at elevated temperatures. This type of combined strengthening from both the matrix and binder provides a new strategy to improve the high-temperature mechanical properties of cemented carbides. Image 1 • The high temperature performance of WC-Ni 3 Al is more excellent than that of WC-Co. • The good performance results from the formation of stacking faults and twins. • Yield loci verified only the prismatic slip is activated under high temperature. • The generation of twins must satisfy three conditions. [ABSTRACT FROM AUTHOR]