Development of coating method of titanium carbide and titanium carbonitride on diamond

• Published in: Precision engineering 2020-09, Vol.65, p.1-6
• Main Authors: Hashimoto, Masaki, Kanda, Kazutaka, Maki, Norio, Koizumi, Masaharu
• Format: Article
• Language: English
• Subjects: Coating method; Diamond; Electroplated diamond tool; Titanium carbide; Titanium carbonitride
• ISSN: 0141-6359; 1873-2372
• DOI: 10.1016/j.precisioneng.2020.04.022

Fracture and drop-off of diamond grains are thought to be suppressed if the diamond grains used, such as those for electroplated wires, are coated with a material having a higher coefficient of thermal expansion than diamond and having good adhesion to the binder metal. In this study, we selected titanium carbide and titanium carbonitride as materials with such characteristics, and investigated their coating methods. The titanium carbide coating was formed by heating a mixture of diamond plate or diamond grains and titanium powder in vacuum at a temperature lower than the melting point of titanium. Titanium carbonitride formation tests were performed in two ways: by forming a titanium carbide coating and titanium carbonitride in the same chamber continuously or by exposing the sample to the atmosphere after titanium carbide formation and subsequently reheating it in nitrogen. The titanium carbide coating was tested by heating the mixture of the diamond plate and the titanium grains in vacuum of 2.0 × 10−3 Pa or less at 1073–1273 K for 60–120 min. For the titanium carbonitride coating, the primary titanium carbide coating was applied at temperatures of 1123–1273 K for 60 min. Then the titanium carbonitride formation was done at the same temperature but with different heating times. Products on the diamond after heating tests were analyzed using X-ray diffraction. Results show that titanium carbide can be coated onto the diamond surface by heating the mixture of diamond and titanium powder in vacuum at 1073 K or at a higher temperature. Results demonstrated further that titanium carbonitride can be formed by heating the diamond plate or the diamond grains coated with titanium carbide in nitrogen at a temperature higher than 1123 K. The titanium carbide layer thickness and the ratio of nitrogen in the titanium carbonitride increased concomitantly with increased heating temperature and increased heating time. •Coating method of titanium carbide (TiC) and titanium carbonitride (TiCN) on diamond.•TiC is formed by heating a mixture of diamond and titanium grains in vacuum.•TiC coating is performed at a temperature below the melting point of titanium.•TiCN is formed by heating TiC coated diamond in nitrogen.