Microcrystalline diamond (MCD), nanocrystalline diamond (NCD) and microcrystalline and nanocrystalline composite diamond (MNCD) films are all deposited on flat square shaped WC-6%Co substrates by using bias-enhanced hot filament chemical vapor deposition (HFCVD) apparatus. The diamond films are characterized with scanning electron microscope (SEM) and Raman spectrum. Typical diamond film features are exhibited in the observation of SEM and the analysis results of Raman spectrum. The tribological properties of diamond films against zirconia ceramic are conducted on a ball-on-plate type rotating reciprocating tribometer in ambient air. The average friction coefficients of MCD, NCD and MNCD film in stable period are 0.205, 0.181 and 0.138 respectively. The images of surface topography based on white-light interferometer suggest a very low wear rate of CVD diamond film.

In this study, micro- crystalline diamond(MCD), fine grade diamond(FGD) and nano- crystalline diamond(NCD) thin films are successfully coated on WC-Co micro drills(φ=400µm) adopting hot filament chemical vapor deposition (HFCVD) technique. The microstructure and cutting performance of micro drills for applying to drill electrical discharge machining(EDM) graphite coated with MCD, FGD and NCD films are systematically investigated by means of field emission scanning electron microscope(FESEM) and Raman spectroscopy. After drilling of 1500 holes, wear behavior of these micro drills is analyzed by FESEM and NCD coated micro drills exhibit minimum flank wear compared with the other samples due to the relatively good wear resistance and friction properties of NCD films.

In the process of HFCVD diamond film growth on the multitudinous micro end mills, the uniformity and stability of the temperature distribution have a vital importance on the quality of film. So a new method by using the finite volume is proposed to analyze the importance of different disposition parameters on the uniformity of substrate temperature field. These parameters are filament diameter (d), filament-substrate distance (H), filament separation (S) and filament length (L). The mono-factor method are used to optimize the best parameter combination. The simulation results show that the optimized parameters are d=0.65mm, H=10mm, S=27mm and L=160mm.

Si-doped diamond films are deposited on cobalt cemented tungsten carbide (WC-Co) welding dies using hot filament chemical vapor deposition (HFCVD) method, where tetraethoxysilane (C8H20O4Si) is introduced in the reactive chamber as silicon source by bubbling method. Filed emission scanning electron microscope (FESEM) and Raman spectroscopy are used to characterize the as-deposited diamond films. The results show that silicon doping can reduce the diamond crystal size and residual stress of diamond films, and also increase the FWHM of first order diamond Raman line. The polishing time of diamond coated welding dies also can be shortened by silicon doping. Si-doped diamond coated welding dies possesses comparable practical application performance with conventional diamond coated welding dies. Compared with the nylon and WC-Co welding dies, the working lifetime of diamond coated welding dies increases 200 and 10 times, respectively.