Papers by Keyword: Diamond Film

Abstract: Diamond films and diamond/graphite composite films have excellent wear resistance, it can be used as the protective coating to effectively improve the parts life and performance. The micro crystalline diamond films, nanocrystalline diamond films and diamond/graphite composite films were prepared on sic substrate by microwave plasma chemical vapor deposition on different power, pressure and CH4 concentration growth parameters. The films surface characteristics were research by SEM and Raman spectrometer. The results indicate that the diamond grain size and content decreased and graphite content increased with CH4 concentration increasing on constant microwave power and cavity pressure; the diamond grain size decreased and graphite constant increased with cavity pressure increasing on constant microwave power and CH4 concentration.

Abstract: Cutting tools of WC-Co are widely used in cutting field. Nevertheless, its wear resistance and lifetime are not qualified for the high performance cutting. Therefore, diamond films are deposited on WC-Co substrates to overcome its disadvantages. In this paper we investigate the effects of the pretreatment on substrates and as-deposited WC-Co samples by using a hot filament chemical vapor deposition (HFCVD) reactor. Prior to deposition, the WC-Co substrates were submitted to surface roughening by Murakami reagent and to surface binder removal by Caro’ acid with varied durations. Surface roughness R_a determined by AFM varied from 110 to 279 nm. The diamond films are characterized by scanning electron microscopy (SEM) and Raman spectroscopy, whose results present a sharp peak at 1336 cm^-1 indicating sp³ diamond. The adhesion between the diamond films and substrates was evaluated by pull-off tests with the highest adhesion strength is 26.92 MPa. Cracked interface is characterized between diamond films and substrates, using SEM and energy dispersive spectroscopy (EDS) to analyze the adhesion performance.

Abstract: The evolution of the CVD diamond coatings morphology after perpendicular direction reactive ion etching was investigated. During the surface treatment, the average surface roughness was reduced. The efficiency of the etching decreases with the increasing of the processing time, until the surface roughness has been reduced by 30±5%. The height points spread over the surface were measured. The quality of the obtained films was investigated using the Raman spectroscopy.

Abstract: This paper presents a study of the influence of cutting conditions (cutting velocity, feed, cutting depth and lubrication) on turning TC11 (Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) titanium alloy. Taguchi methodology design was adopt for carrying out experiments. Turning process parameters such as cutting speed, feed rate and depth of cut were varied to study their effect on process responses such as cutting force (Ft), surface roughness (Ra) and temperature on cutting zones (T). Minimum quantity lubrication (MQL) technology was adopt to increase the lubricating and cooling effect. Meanwhile, CVD diamond coating was deposited on the cemented carbide insert to reduce its friction with workpiece and increase its wear resistance. From the analysis of orthogonal tests, depth of cut contributes the most for the main cutting force and cutting temperature, while feed rate had the most significant effect on surface roughness on the workpiece. MQL can reduce the cutting temperature at the cutting zones, especially for the uncoated cutting inserts whose temperature decreases by an average of 60~80°C. The cutting force, surface roughness and cutting temperature of CVD diamond coated inserts were all higher than those of uncoated tools, especially with MQL lubrication. Considering the cutting efficiency and cost, the optimal parameters in the turning process of TC11 for minimizing the cutting force, surface roughness and cutting temperature are obtained as Vc=115m/min, f=0.08mm, a_p=0.5mm under MQL lubricating with uncoated cemented carbide as the cutting tool.

Abstract: In this paper, the drawing die of cemented carbide WC-Co (Wolfram Carbide-Cobalt) was taken as the substrate which was preprocessed by Murakami solution and aqua regia. DCS (Direct Current Magnetron Sputtering) was adopted to sputter the Nb interlayer in the bore of the drawing die. By using EACVD (Electron Assisted Chemical Vapor Deposition), micro-nanocomposite coating was deposited. Then, specimens were characterized through methods like SEM (scanning electron microscope) and Raman etc. Results indicated that the drawing die showed very smooth coating surface and a compact, uniform structure; the grain size < 50 nm and surface roughness < 10 nm. It can be inferred from the indentation experiment that there was satisfactory adhesion force between coating and the substrate. So, the drawing die can satisfy the working requirement of drawing wires.

Abstract: In the present study, high-quality chemical vapor deposition (CVD) micro-crystalline diamond (MCD) film was successfully deposited on the surface of the Φ0.5 mm×120 mm tungsten wire using a special designed graphitic jig for supporting the substrate and a two-step deposition procedure for guaranteeing the uniformity of as-deposited diamond film. It is proved that as-deposited film indeed presented much more uniform thickness than that obtained using a conventional jig described in the previous literature, and a very thick WC interlayer spontaneously formed between the substrate and the diamond film, which together with as-deposited MCD film have significant effects on mechanical properties of the wire. Generally speaking, the coated wire remains extremely high surface hardness of the MCD film and considerable toughness of the substrate, along with favorable film-substrate adhesion. It is recognized that these the coated tungsten wires have broad application prospects, but the technologies for depositing diamond films that are thick enough on even longer and thinner wires still need further investigation.

Abstract: In this work, the achievement and characterization of boron-doped nanocrystalline diamond films is presented. A series of experiments varying boron doping levels from 2,000 to 30,000 ppm and film growth times during 6, 10 and 16 h were performed. These films were analyzed by Scanning Electron Microscoy (SEM), Atomic Force Microscopy (AFM), Raman spectroscopy and Cyclic Voltammetry (CV) measurements. The results showed that the films presented two morphologies: ultra and nanocrystalline diamond. From Raman spectroscopy, the doping level increase for all the films, independent of growth time, increased the boron acceptor number and it was confirmed by Mott-Schottky plot (MSP). Electrochemical response showed the influence of boron content in the work potential window, mainly for films grown during 6 h. However, the reversibility was almost independent on the boron content for samples grown during 16 h.

Abstract: 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.

Abstract: The CVD diamond films have a series of excellent performances, so it has a wide range of applications in the cutting tools, wearable devices, electrochemical electrodes and other fields, and it has a very substantial market prospects. In this study, The diamond films with a layer of uniform and smooth were deposited on the surface of the complex surface YG6 carbide end mill by using the hot filament CVD method, the quality of diamond films was detected by using the scanning electron microscopy and the laser Raman spectrometer. The cutting performances of diamond coated end mill were evaluated from the workpiece surface quality and tool life two aspects by cutting silicon carbide aluminum reinforced composites, and compared with the uncoated carbide tools. The experimental results show that because of the cutting tool was pretreated that make tool surface coarsening, leading the surface quality was machined by diamond coated tools is lower than the carbide cutting tools. However, the coating can protect the tools, increase the wear resistance of the coated tools and make the life of the diamond coated tools increase 3-5 times than the carbide cutting tools.

Abstract: A simple, fast, and reliable characterization method for measuring junction temperature (Tj) on high power GaN-based light emitting diodes (LED) was presented in this study. Thermal characteristics of high power Light-emitting-diode have been analyzed by using a three-dimensional thermal conduction model. Maximum operation temperature has also been calculated. The induced thermal behaviors of the best package processes for LED device with diamond film were investigated by finite element analysis (FEA) and by experimental measurement. The large change of forward operation voltage with temperature in light emitting diodes is advantageously used to measure junction temperature. Using this method, junction temperature (Tj) of LED under various structures and chip mounting methods was measured. It was found that the junction temperature can be reduced considerably by using diamond film substrates to replace sapphire substrate. In this study, the junction temperature can be decreased by about 14.3% under 1.5W power and decreased by about 15.9% under 1W power for 1mm square die. The thermal resistance (RT) can be measured to be 14.8°C/W under 1.5W power and 16.6°C/W under 1.W power.