Improvement of adhesive strength and surface roughness of diamond-coated thin film tools

The adhesion strength and surface roughness of diamond films are the key factors to affect the cutting performances of diamond coated tools. The diamond thin films are deposited on WC-Co cemented carbide substrates using the acetone and hydrogen as the gas source by the electronically aided hot filament chemical vapor deposition(EACVD). The surface pretreatment methods for WC-Co cemented carbide substrates are the key factors to improve the adhesion strength of diamond film. CVD processes are very important for lowing diamond film roughness. On the basis of the analysis of the influences of the pretreatment methods and CVD process parameters on mechanical properties of diamond-coated thin film tools, a new pretreating method using Ar-H-2 etching decarburization by microwave plasma was performed for the substrate surface, and a new technique controlling deposition procedure was developed for CVD process. The effect of the new pretreating method and CVD process on the morphology, adhesion strength, surface roughness, tool life and the cutting performances of diamond-coated tools were investigated. The research results show that the pretreatment process using Ar-H-2 etching decarburization by microwave plasma was an effective method to enhance the adhesive strength, and the surface roughness of diamond thin films could be decreased by appropriately controlling reactive gases pressure. It is of great significance for improvement of cutting performances of diamond-coated tools of the new technology of depositing diamond thin film with the low surface roughness and high adhesion strength on the cemented carbide substrates.