Microstructure and mechanical properties of WC–TiC–Co cemented carbides produced by spark plasma sintering (SPS) method

Abstract

Cemented carbide 91 wt% WC–3 wt% TiC–6 wt% Co was sintered by spark plasma sintering at different temperatures of 1200 °C, 1300 °C, and 1400 °C and the effect of sintering temperature on the microstructure and properties of this type of composites, such as total density, apparent density, hardness, and fracture surface were measured and observed using Field Emission-Scanning Electron Microscopy, Optical Microscopy, X-ray diffractometry and mechanical test instruments. The results showed that the apparent density of the samples increased with increasing sintering temperature from 1200 to 1300 °C from 13.98 to 14.23 g/cm3, respectively. But in the sample sintered at 1400 °C, the density was reduced to 14.20 g/cm3. An increase in the fluidity of the cobalt phase and capillary pressure is the cause of the increase in density at higher temperatures, the cobalt phase has evaporated and the density has decreased slightly. Also, Vickers micro-hardness results showed that the hardness of sintered samples increased with the increase of sintering temperature. For the sample sintered at 1200 °C the hardness value of 1746.41 kgf/mm2 was obtained which increased with increasing sintering temperature from 1300 to 1400 °C from 2094.33 to 2280.97 kgf/mm2, respectively. The amount of core–shell structure [including TiC-core and (W, Ti)C-shell] increased with increasing the sintering temperature process. As a result, the hardness also increased. At the optimum sintering temperature, it was found that TiC inhibited the grain growth of tungsten carbide. In addition, as expected, the grain growth of tungsten carbide increased with increasing sintering temperatures. Examination of the fracture surface of sintered samples at different temperatures also showed that brittle fracture involves fracture.