MATCHING OF PARTICLE SIZES OF WC/Co POWDERS AND SPARK PLASMA SINTERING DENSIFICATION
WC/Co粉体粒径匹配与放电等离子烧结致密化

The particle size of raw powders to prepare the cemented carbides plays a significant role not only in the properties of the resultant bulk material, but also in the sintering process. WC/Co composite powders with various size matches were prepared by spark plasma sintering (SPS), and the variations of shrinkage rate, which is an important factor describing SPS process, with the sintering temperature and the relationship between the shrinkage rate and the relative density of the sintered sample were analyzed. The results show that the temperature of shrinkage starting, the temperature corresponding to the peak of the shrinkage rate, and the temperature of full densification are almost the same for different sized WC particles, however, all of the above temperatures reduce with the decrease of the Co particle size. It indicates that the shrinkage process of SPS has a rather very weak relationship with the WC particle size, whereas has a close relationship with the Co particle size. As compared with the conventional sintering methods, the above temperatures and the relative density corresponding to the maximum of the shrinkage rate are all lowered. It implies that in the conventional process, at the stage with the maximum of the shrinkage rate, most of the shrinkage has been accomplished. However, in the SPS process, at the same stage the shrinkage degree is lower. Finally, he secial SPS mechanisms for comosite powders with various size matces were analyzed.