Graphitization of Diamond Crystals in the Manufacturing of Diamond–SiC–Si Composite

— The graphitization of diamond single crystals with a grain size of 200–250 µm was studied when heated to 1000–1300°C. During the production of diamond–SiC composites by vacuum siliconization of a porous diamond matrix, not only the surface graphitization of diamond grains, but also the graphitization of the diamond at internal defects occurs. A decrease in the average strength of a single grain of diamond crystals as a result of their heat treatment both in an inert medium and during vacuum siliconization was demonstrated. It was found that siliconizing at a furnace temperature of 1550°C, despite the short process time, leads to a significant (40%) drop in the strength of diamond crystals. At the same time, within the diamond mass there are always individual grains that have retained their strength during the heat treatment process.