Papers by Keyword: CVD Diamond Film

Abstract: The tribo-map of typical CVD diamond film exhibiting the interaction between the wear rate, friction coefficient and friction conditions would help optimize the working parameters of CVD diamond film coated tools and wear-resistance components. The tribological behaviors of CVD diamond films sliding against Si₃N₄ balls were studied by conducting a group of tests on the ball-on-plate type reciprocating friction tester under several sliding speeds and normal loads in the ambient air. The examined MCD films and NCD films were deposited on square flat WC-Co substrates. The worn surfaces on the diamond films were observed by SEM and the wear volumes of diamond films were measured by surface profilometer. The results indicated that the influences of the sliding speeds and normal loads on the friction coefficients for both MCD films and NCD films were obvious. When the load was 6 N, MCD film obtained the lowest friction coefficient of 0.11 at the sliding velocity of 0.2 m/s, while for NCD film the minimum value was 0.07 as the sliding speed was 0.13 m/s. The wear rate of the MCD film decreased as the load improved, while for the NCD film, the tendency was just the opposite. The influence of sliding speed on the wear rate of the MCD films was not distinct, while for the NCD films, the sliding velocity greatly affects their wear rate. The wear rates of most NCD films were around 0.2×10^-7 mm³/Nm, while those of the MCD films fluctuated from 0.6×10^-7~1.6×10^-7 mm³/Nm. To elucidate the effect of operating environment on wear mechanism of diamond/ Si₃N₄ tribo-pair, the tribo-map was developed.

Abstract: This paper investigates the applicability of the dynamic friction polishing (DFP) technique to process the chemical vapour deposition (CVD) diamond surfaces. Two types of CVD diamond specimens were studied. A stepwise polishing process was introduced to minimise the cracking in CVD thin films. The investigation focused on the polished surface quality in relation to the polishing conditions and material remove rates. It was found that by selecting proper polishing parameters, surfaces of quality finish with a roughness of less than 70 nm Ra could be obtained in 15 minutes when the specimens were CVD diamond wafers with an initial roughness of 17 μm. The polishing time could be reduced to only 2.5 minutes in the case of diamond thin film specimens of initial roughness of 1.6 μm.

Abstract: This paper deals with a new surface finishing method of electrically conductive diamond materials by making efficient use of an electrically conductive nature of the workpiece material, instead of conventional methods such as grinding, lapping and polishing using diamond abrasives. The authors focused on the electrolytic machining method and not on the electro discharge machining method for the two advantageous features of the electrolytic machining in addition to the general view that a better surface roughness could be obtained. One of those features is that no higher heat is generated at the machining point. This can eliminate a risk of the film delamination in the case where a workpiece is the CVD diamond coated tool. The other is that a wider machining gap is available between an electrode and a workpiece. This was thought to allow the electrolytic machining to be applied to a tool with a complex shape such as a drill and an endmill. Based on these concepts, electrolytic machining experiments were conducted on the electrically conductive diamond materials. From the results, it was found that the surface of the electrically conductive diamond could be smoothened enough by electrolytic machining though relatively long period of time was required.

Abstract: CVD diamond has become the mainstream trend for the development of diamond. Its ultra precision machining is one of the key technologies for expanding the application of CVD diamond film. The efficient polishing method is studied, called accelerant polishing technology, which can lower the activation energy needed in diamond graphitization by the accelerant action of transition metal. It accelerates reaction rates of graphitization and promotes the implementation of diamond’s removal mechanism. Experimentation results indicate that the polishing method is one new type of precision polishing technology with low cost and high efficiency.

Abstract: A new setup for polishing of diamond films on a high speed rotating stainless plate has been developed, and a rare earth metal plate was used to clear the carbon atoms diffused into the polishing plate. The surface morphology and clearance mechanism were studied by using scanning electron microscopy and X-ray photo-electron spectroscopy before and after polishing, respectively. The results showed that the chemical reaction between the rare earth metal and carbon diffused into the polishing plate took place and the rare earth metal could clear the carbon element effectively during the super-high speed polishing.

Abstract: Super-high speed polishing of diamond film is a newly proposed method due to its outstanding features such as low cost and simple apparatus. The interface temperature rise is due to the friction force and the relative sliding velocity between the CVD diamond film and the polishing metal plate surface. In this paper, the interface temperature rise in super-high speed polishing of CVD diamond film was investigated by using the single-point temperature measurement method. Additionally, the influence of polishing plate material on the characteristics of super-high speed polishing has been studied. The results showed that cast iron is not suitable for super-high polishing, while both 0Cr18Ni9 stainless steel and pure titanium can be used for the super-high polishing of CVD diamond film. The quality and efficiency of polishing with 0Cr18Ni9 stainless steel plate is much higher than those of pure titanium, and the material removal rate could reach to 36-51 m/h when the polishing speed and pressure are 100 m/s and 0.17-0.31 MPa, respectively.

Abstract: The friction behaviors of CVD diamond films on silicon nitride substrates are investigated comparing with the uncoated silicon nitride samples. Two types of CVD diamond films, namely MCD and NCD films, are deposited on the silicon nitride substrates using HFCVD method, and then SEM, while light interferometer, XRD and Raman spectra are employed to characterize as-deposited diamond films. The friction tests are carried out in a ball-on-plate reciprocating friction tester, with ball-bearing steel, copper, tungsten carbide and tungsten carbide as the counterpart materials. The results show that the diamond film deposited on silicon nitride substrate has significant effect on reducing the friction coefficient and enhancing the wear resistance. The friction coefficients of MCD and NCD films are around ~0.35 in dry sliding against ball-bearing steel and copper, while for sliding with the tungsten carbide and silicon nitride, the friction coefficients of NCD films even decrease as low as ~0.12 and ~0.08 respectively. The special wear rate of the silicon nitride and NCD film can be estimated as 6.2167×10-5 mm3 N-1 m-1 and 4.03×10-7 mm3 N-1 m-1 with the counterface of silicon nitride. Comparatively, no measurable wear occurs on the worn surface of the MCD film.

Abstract: The in-process sharpening mechanism of the grinder during the grinding process of a CVD diamond film surface is investigated using the composite electro-plating in-process sharpening (CEPIS) technique. The bath concentration is employed to investigate the variation of coating structure deposited on the grinder. Results show that the land area ratio increases with increasing nickel chloride concentrations (NiCl2．6H2O) of the plating bath from 10 to 30 g/L, and the coating structure becomes very smooth without porous area at the nickel chloride concentration of 75 g/L. Therefore the coating structure becomes compact to hold the diamond particles rigidly. Consequently, the grinding ability of the grinder can be significantly improved, where the mirror-like surface of the CVD diamond film can be achieved.

Abstract: The fast development of SAW requests higher quality surface of CVD diamond films. Nowadays the mechanical lapping method is one important way to polish CVD diamond films, but the processing cost is high due to the low machining quality and efficiency. This paper reports a new accelerant lapping technology base on mechanical lapping and exploratory studies the role of three kinds of metal of the iron, titanium and nickel in the process of lapping. Firstly, ANSYS/LS_DYNA was used to simulate the process of friction and cutting between the CVD diamond films and abrasive plate of different material to analyze the temperature distributing on the interface and weather it is helpful for lapping. Then, experiment researches were carried out using the abrasive plate with different accelerant materials ratio. The results indicate that titanium is the most potent accelerant for polishing, followed by iron and then nickel. Experimental study also found that the accelerant lapping can carried out effectively by using the abrasive plate made of different metallic materials as accelerant to the diamond film grinding.

Abstract: Accelerant polishing is a new polishing technique based on the principle of diamond graphitization. It makes full use of the catalysis of transition metal such as Fe, Ti. In this paper, it researches on the trend of the graphitization of CVD diamond film at different temperature by DTA, TG, DTG and Raman spectra analysis. The results show that accelerant polishing technique can reduce the required conditions of graphitization, and carry out the graphitization reaction at a low temperature.