Fabrication and application of high quality diamond-coated tools

Diamond-coated tools were fabricated using Co cemented carbide inserts as substrates by electronically aided hot filament chemical vapor deposition (EACVD). An amount of additive in an acid solution was used to promote the Co etching of the substrate surface. The surface of the WC–Co substrate was decarburized by microwave plasma with Ar–H2 gas. The effect of the new substrate pre-treatment on the adhesion of the diamond films was investigated. A boron-doped solution was brushed on to the tool surface to diffuse the boron into the substrate during diamond deposition. A new process was used to reduce the surface roughness of the diamond thin films by appropriately controlling the deposition parameters, which consists of a composite diamond film chemical vapor deposition procedure including first the deposition of rough polycrystalline diamond and then fine-grained diamond. The research results show that the pre-treatment, including both Co etching in acid solution and Ar–H2 etching decarburization by microwave plasma, is an effective method to enhance the adhesive strength. An adequate amount of boron dopant solution can effectively suppress cobalt diffusion to the surface and avoid the catalytic effect of Co at high temperature. The composite film CVD process can deposit smooth diamond films with low surface roughness. It is of great significance for the improvement of the cutting performance of diamond-coated tools to use the above new technology to deposit diamond coatings with low surface roughness and high adhesive strength on WC–Co substrates.