Effect of Ni addition on pressureless sintering of tungsten diboride

WB2 ceramic was prepared by a two-step-sintering method. First, phase-pure WB2 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 degrees C, 1 h, in vacuum). Second, WB2 powder with Ni was used as a sintering aid (1500 degrees 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 WB2 ceramic can be optimised by adjusting the content of sintering aids. The best performance of the WB2 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. (C) 2013 Elsevier Ltd. All rights reserved.