Abstract:
Tungsten carbide-cobalt (WC-Co) cemented carbides, as an important type of powder metallurgy products, are widely used in numerous industrial fields. Traditional sintering methods suffer from high sintering temperatures, long sintering times, and grain coarsening, which make it difficult to meet the requirements for the preparation of high-strength fine-grained cemented carbides. In this study, the sintering behavior of sub-micron WC-5Co (with a mass ratio of cobalt of 5%) cemented carbides was investigated using the high-temperature and high-pressure (HTHP) method. The experimental results show that under the treatment conditions of 5.0 GPa and 1250 °C, the sintered body can achieve a relative density of 99.4% and a Vickers hardness value of 24.0±0.3 GPa, which is significantly better than that of the same composition of cemented carbides prepared by spark plasma sintering (SPS) and vacuum sintering methods. Compared with the commercial cemented carbides with the same initial powder, the average grain size of WC in the sintered samples under high-temperature and high-pressure conditions is reduced by about 36%, and the Vickers hardness is increased by about 10%. Compared with traditional sintering methods, the HTHP sintering method effectively reduces the sintering temperature and improves the sintering efficiency. Moreover, high pressure can effectively inhibit the abnormal growth of WC grains during solid-state sintering. During liquid-phase sintering (at 1450 °C), with the increase of sintering pressure, the WC grains are significantly refined. When the sintering pressure is increased from 3.0 GPa to 5.0 GPa, the Vickers hardness of the samples is increased by about 7%.
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