Strength of diamond - silicon carbide interfaces in silicon carbide bonded diamond materials containing graphitic interlayers

The properties of composite materials strongly depend on the bonding between the reinforcement particles and the matrix phase. High strengths of the diamond/SiC interface have recently been reported for silicon carbide bonded diamond materials. Due to the metastable character of diamond under manufacturing conditions, graphite interlayers can form within the diamond/SiC interface. In order to investigate their influence on the strength of the interface, a material with intentionally generated graphitic interlayers was prepared and microcantilevers were cut by focused ion beam milling (FIB) at the SiC/graphite-interlayer/diamond interface. By insitu bending experiments inside a scanning electron microscope (SEM), a mean value of 7.0 +/- 1.2 GPa was obtained as interface strength, which is only slightly lower than the value of graphite-free SiC/diamond interfaces. These values are indicative of direct covalent bonding of the graphitic layers to the diamond reinforcement particles. The results show that thin graphitic interlayers have only little effect on the properties of SiC bonded diamond materials.