Control of the SiC Polytypes in SiC Bonded Diamond Materials

Silicon carbide-bonded diamond materials produced by pressureless reaction infiltration of diamond preforms have high wear resistance and thermal conductivity, making them ideal for a range of industrial applications. During infiltration, the Si is typically converted to cubic β-SiC. The aim of the work was to investigate the extent to which the formation of hexagonal α-SiC can be achieved by adding α-SiC or AlN nuclei to the preform. Detailed microstructural investigations using XRD, high-resolution FE-SEM, and EBSD analyses show that both AlN and SiC serve as nuclei for α-SiC. Regardless of this, a large proportion of β-SiC forms on the surface of the diamonds. However, the added nuclei change the structure of the SiC framework that forms.