For diamond/metal composites it is better to use diamond particles coated with metal carbide because of improved wettability between the diamond particles and the matrix. In this study, the coating of diamond particles with a chromium carbide layer is investigated. On heating diamond and chromium powders at 800~900 oC in molten salts of LiCl, KCl, CaCl2, the diamond particles are coated with Cr7C3. The surfaces of the diamond powders are analyzed using X-ray diffraction and scanning electron microscopy. The average thickness of the Cr7C3 coating layers is calculated from the result of the particle size analysis. By using the molten salt method, the Cr7C3 coating layer is uniformly formed on the diamond particles at a relatively low temperature at which the graphitization of the diamond particles is avoided. Treatment temperatures are lower than those in the previously proposed methods. The coated layer is thickened with an increase in heating temperature up to 900 oC. The coating reaction of the diamond particles with chromium carbide is much more rapid in LiCl-KCl-CaCl2 molten salts than with the molten salts of KCl-CaCl2.

Several boride sintered bodies such as , , and were previously reported. In the present study, the sinterability and physical properties of chromium boride containing chromium carbide sintered bodies were investigated in order to determine its new advanced material. The samples were sintered at desired temperature for 1 hour in vacuum under a pressure by hot pressing. The relative density of sintered bodies was measured by Archimedes' method. The relative densities of addition of 0, 5, 10, 15 and 20 mass% composites were 92 to 95%. The Vickers hardness of the with 10 and 15 mass% composites were about 14 and 15 GPa at room temperature, respectively. The Vickers hardness at high temperature of the addition of 10 mass% composite decreased with increasing measurement temperature. The Vickers hardness at 1273 K of the sample was 6 GPa. The Vickers hardness of addition of composites was higher than monolithic sintered body. The powder X-ray diffraction analysis detected CrB and phases in containing composites.