Nanocrystalline diamond films were deposited on Co-cemented carbide substrates using acetone/ H2/Ar gas mixture by bias-enhanced hot filament chemical vapor deposition（HFCVD） technique.The evidence of nanocrystallinity,smoothness and purity was obtained by characterizing the sample with scanning electron microscopy（SEM）,X-ray diffraction（XRD）,Raman spectroscopy,atomic force microscopy （AFM ）,and field emission transmission electron microscopy（FE-TEM ）.The results show that nanocrystalline diamond films consists of nanocrystalline diamond grains with sizes range from 20 to 80 nm and contain a large amount of grain boundaries.The surface roughness of the films is measured as Ra<50nm.The Raman spectroscopy,XRD pattern,and FE-TEM image of the films indicate the presence of nanocrystalline diamond.A new process is used to deposit composite diamond coatings by a two-step chemical vapor deposition procedure,including first the deposition of the rough polycrystalline diamond and then the smooth fine-grained nanocrystalline diamond film.Such composite diamond coatings not only display good adhesion and wear resistant properties,but also have smooth surfaces that are liable to polishing.This coating technology can not only meet the requirement of the adhesion of diamond coatings,but also reduce surface roughness of diamond coatings effectively,thus remove the obstacles for the industrialization of CVD diamond coatings.The diamondcoated dies with these composite coatings show obvious effect in the practical application.
Sun Fanghong~1,Zhang Zhiming~2,Shen Hesheng~2,Guo Songshou~2 (1.School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai 200240,China
