Improvement of adhesive strength and surface roughness of diamond films on Co-cemented tungsten carbide tools

摘要

Diamond-coated tools were fabricated using Co-cemented carbide inserts as substrates by the bias-enhanced hot filament chemical vapor deposition. The surface of the WC-Co substrate was decarburized by microwave plasma with Ar-H_2 gas. Effect of the new substrate pretreatment on the adhesion of diamond films was investigated. A boron-doped solution was brushed on the tool surface to diffuse boron into the substrates during diamond deposition. A new process was used to lower the surface roughness of diamond thin films by appropriately controlling acetone concentration and reactive gases pressure. It consists of a two-step chemical vapor deposition procedure that includes, first, the deposition of the rough polycrystalline diamond and then the fine-grained diamond. The research results show that the pretreatment using Ar-H_2 etching decarburization by microwave plasma is an effective method to enhance adhesive strength. An adequate amount of boron dopant solution can effectively suppress the cobalt diffusion to the surface and avoid the catalytic effect of Co at the high temperature. Smooth diamond films with low roughness can be deposited by the two-step CVD process. It is of great significance for improvement of the cutting performance of diamond-coated tools using the above new technology to deposit diamond coatings with the low surface roughness and high adhesive strength on WC-Co substrates.