Influence of novel sintering process on the densification and microstructures of ceramic composite materials

Generally, a fully dense ceramic material must be fabricated at very high temperature or pressure even by the hot pressing process. In this study, a novel hot pressing process was proposed in order to improve the densification and hardness of ceramic tool materials. Synthetic graphite powder was used in the novel process to replace graphite paper as a lining material. The sintering temperature of SiC whisker toughened ceramic materials can be lowered by 150 °C. The experimental trials showed that the relative density and Vickers hardness of the ceramic materials were remarkably improved. The greatest improvement was 23.78% in Vickers hardness increasing from 18.00 ± 0.60 GPa to 22.28 ± 0.38 GPa. The homogeneous and densified microstructures were obtained because of the good air permeability of synthetic graphite powder. At the end of the sintering process, the synthetic graphite powder was still in the powder form and was easy to remove from the sintered body. The novel process can solve the problem of densification of the difficult-to-sinter ceramic materials, providing an effective solution in preparing high-density ceramic tools.