The adhesive strength and surface roughness of diamond films are the key factors to influence the cutting performance and tool life of diamond-coated tools. Compared with the sintered polycrystalline diamond, the deposited thin film diamond has the great advantage on the fabrication of cutting tools with complex geometries. Because of their low costs for fabrication equipment and high performance on high speed machining non-ferrous metals and alloys, metal-compound materials, and hard brittle non-metals, diamond-coated drills find great potentialities in the commercial application. However, the poor adhesion of the diamond film on the substrate becomes the main technical barriers for the successful development and commercialization of diamond-coated tools. In this paper, diamond thin films were deposited on WC-Co based drills by the electron aided hot filament chemical vapor deposition (EACVD). A new multiple chemical pretreatment technology including microwave oxidation, reaction in alkaline solution and cleaning by ultrasonic treatment in acid solution was developed and affects on the diamond adhesion strength, nucleation and surface morphology were investigated. At the same time, a special setup to fabricate diamond-coated drills was also developed and then the novel CV]D process based on the varied parameters controlling model was presented, therefore the uniform quality and homogenized thickness of diamond coating could be available. Composite diamond films were achieved by firstly depositing the rough polycrystalline diamond layers which had good adhesion, and then overlapping the smooth diamond layers with nanometer size grains which yielded very low roughness. From practical utilization viewpoint, the cutting performance of the diamond coated drill was studied by drilling SiC particle reinforced aluminum matrix composite. The satisfied wear resistance and decrease of torque and thrust lead to the long tool life of the diamond coated drills. This paper exhibits the meaningful work for the development of cutting tools with complex geometries and further extends application of diamond material.
