Effect of Graphite Addition on the Microstructure, Mechanical Properties and Oxidation Resistance of HfB2-SiC Composites Prepared by the SPS Method

In this study, HfB2-SiC-graphite composites were fabricated using spark plasma sintering at 1900 ℃ for 10 min. The effect of graphite content on the microstructure and mechanical properties was studied; also, oxidation resistance of the prepared composites was investigated at 1400 ℃ for 32 h. Weight changes and thickness of the formed oxide layer were measured. The relative density, toughness and strength of the SPSed composites increased with raising graphite up 2.5 wt% and then decraesed. On the other hand, the hardness of the composites was decreased when graphite was added. Oxidation resistance of the composites was, thus, improved following graphite addition up 2.5 wt%, while the ecessive quantity of graphite caused poor oxidation resistance of the composites.