Preparation Of CVD Diamond Coated Tools

Diamond film used as a coating is important for machining titanium, aluminum-silicon alloys and composite materials. Diamond coated tools which take advantage of their high hardness, high wear resistance, low friction coefficient, high thermal conductivity, etc. combined with the toughness of cemented tungsten carbide become ideal tools for machining. Therefore, developing of diamond coated tools becomes particularly important. In this thesis, H2 and methane(CH4) were used to deposit diamond film on cemented tungsten carbide substrate by Electronic-assistant hot filament CVD (EA-HFCVD). Scanning electron microscopy (SEM), Raman scattering analyses and cutting tests were performed to characterize the morphology, composition and mechanical properties of the deposited films. H2 and tetramethylsilane(TMS) were used as the precursor gas to deposit SiC film on Si substrate by EA-HFCVD. SEM. X-ray diffraction (XRD), EPMA, Raman scattering analyses and nanoindentation experiments were performed to characterize the morphology, phases, composition and mechanical properties of the deposited SiC film. SiC and diamond films were deposited on cement tungsten carbide (YG6X) substrate. SEM. XRD and Raman scattering analyses were performed to characterize the morphology, phases and bond forms of the deposited films. The conclusions in the work are as follows:(1) Experiments prove that high quality diamond coating can be deposited on cement tungsten carbide drills. The matrix can effect the quality of diamond thin film deposited on cemented tungsten carbide drills. On the one hand the substrate surface processing defects are significantly reflected on the diamond film, on the other hand the matrix binder phase Co and impurity elements result in many impurity phases after film deposition. Co element catalyzes the growth of graphite. Impurity elements form impurity phases. And all these effects are concentrated on the position of the drill cutting edge, which decrease the quality of the cutting edge. The diamond coating drills showed superior cutting performance compared with the uncoated drills when cutting the carbon fiber reinforced composite material. The drill performance showed best when the drilling rate is 20000 rpm. And the film is not peeled after cutting.(2) By increasing the filament current to 45A. we got a dense SiC films on Si wafer. The temperature and the pressure have a significant impact on the growth of SiC. The lower is the pressure, the better is the adhesion of the film and the higher of the intensity. (3)A dense SiC film can be prepared on YG6X cement tungsten carbide inserts. The formation of CoSi phase in SiC deposition process can conduct to stop the diffusion of Co. We got high quality diamond film by using SiC interlayer.