Cemented Carbide Substrate / Hfcvd Diamond Film Preparation And Film Texture Research

Diamond thin film is extensively applied to the various wear-resisting coatings because of its exceptional mechanical properties. Diamond film coated cemented carbide tools had been the mainstream of applied research. But, the poor adhesion between the coatings and substrate restricted the industrialization of diamond coated inserts. In this work, diamond film was deposited by hot filament chemical vapor deposition(HFCVD) on 6 wt.% Co-cemented tungsten carbide (WC-Co). The research regulate the best parameters of diamond films deposition on cemented carbide by the control of HFCVD processing parameters. The aim of this paper is to prepare the diamond films with high adhesion strength and preferential orientation's crystalline grain, which is significant to the implemention of HFCVD diamond coated tools with high efficiency and high-accuracy machining. Conclusion can be drawn as following:(1)The methane concentration is very important effect on the surface roughness and the adherence strength of diamond films. The crystalline form is well-shaped, However, the film is high surface roughness and high defect density due to low nucleation density and low growth rate when the methane concentration is lower. The crystal grain is thin and the morphology is homogeneous due to re-nucleation when the methane concentration is higher. The film's adherence is very poor if the methane content is too high or too low. When the substrate temperature is too hign or too low ,the adhesion is very poor. The adherence strength is best in the case of 690℃. The adhesion is better when the pressure is 30 Torr.(2) With the same deposition temperature,(110) and (110) texture of diamond film is intimately correlated to the value of methane concentration. With the increasing of methane content, (110) facet is strongly preferential orientation. But, when methane concentration isequal to 3.3 percent, diamond film has (100) texture, with the increasing of temperature, the film crystal shape is perfect and the pureness is high. However, crystal grain is more coarse and the surface is more rough when the methane concentration and the pressure is same. The grain orientation of diamond films converts from (110) facet to (111) facet.(3) With the same surface pre-treatment, when the substrate temperature is 690 °C and the pressure is 30 Torr, the preferential textured diamond film is formed as well as the best adhesion if the methane concentration is 3.3 percent. The diamond film with low roughness is formed if the methane concentrate is 5 percent, but, the adherence strength is worse.