Effect of Ni addition on pressureless sintering of tungsten diboride

Abstract WB 2 ceramic was prepared by a two-step-sintering method. First, phase-pure WB 2 powder was successfully synthesised by solid-state reaction using tungsten and boron powder with a molar ratio of 1:2.5. The mixed powders were treated by pressureless high-temperature synthesis (1500 °C, 1 h, in vacuum). Second, WB 2 powder with Ni was used as a sintering aid (1500 °C, 1 h, in vacuum), and the influence of the content of sintering aids on the density, porosity, phase and microstructure was studied. The relationship between Vickers micro-hardness, flexural strength and microstructure was also investigated. The result showed that the properties of the WB 2 ceramic can be optimised by adjusting the content of sintering aids. The best performance of the WB 2 ceramic is obtained using a sintering aid content of 5 wt.%; the relative density, porosity, Vickers micro-hardness and flexural strength of the sintered sample can reach 91.80%, 3.30%, 2623 MPa and 170 MPa, respectively.