Papers by Keyword: Diamond Coating

Abstract: This paper addresses the unique challenges in processing aluminum materials within metal forming technology, specifically focusing on complex wear conditions involving abrasion and adhesion. A promising research approach to avoid abrasive and adhesive tool wear and reduce the friction coefficient towards aluminum alloys is the use of sufficiently smooth CVD diamond coatings. To achieve this, two approaches are considered. First, wear resistance is enhanced by using tool inserts made of carbide or a tungsten alloy, directly coated with CVD diamond. Second, the friction coefficient is selectively influenced or reduced by refining the polished CVD diamond coating through laser ablation. The study investigates the impact of these surface treatments on friction coefficients during both dry and lubricated forming processes involving the aluminum alloy EN AW-5182. Comparative analyses of various surface treatments are conducted against reference tests using diamond-like carbon (DLC)-coated tools. Through application-oriented strip drawing tests, the paper systematically examines how different surface smoothing techniques affect the coefficient of friction. This research provides valuable insights into optimizing metal forming processes for aluminum alloys through tailored surface treatments, advancing our understanding of friction dynamics in these specific manufacturing conditions.

Abstract: In the CH₃Cl/H₂ atmosphere, the adsorption process of various active chlorocarbon groups (CH₂Cl, CHCl, CCl) and CH₃ on the surface of clean diamond used density functional theory (DFT) calculations during CVD process. The reaction heat and activation energy of the active sites on the adsorption reconstituted surface of D-CH₃ and D-CH₂Cl were calculated by transition state search to explore the actual effect of the carbon chloride active group on the surface of CVD diamond (100).The results showed that the adsorption capacity of CHCl, CH₂Cl and CCl on the substrate was gradually weakened and the adsorption energy of CH₂Cl and CH₃ was close. Both CHCl and CH₂Cl could form diamond bonds with the substrate carbon atoms to directly promote the growth of the diamond coating. Since the C-Cl bond was weaker than the C-H bond, the adsorption recombination surface of CH₂Cl generated an energy barrier of the active site lower than the adsorption reconstitution surface of CH3. Therefore, using CH₃Cl/H₂ as a gas source could effectively reduce the energy required for diamond coating growth.

Abstract: The process of producing active vacancies on a hydrogen-terminated diamond surface is the most important rate-limiting stage in CH₄/H₂ and CH₄/H₂/CO₂ atmospheres. Hydrogen atom and the hydroxyl group can bone to the hydrogen atom on the diamond surface and create an active vacancy. Density functional theory (DFT) was used to study the extraction reaction by two reactants both hydrogen atom and the hydroxyl group. The result indicated that the hydroxyl group could reduce the energy required for diamond surface activation. What is more, the activation rate of the surface by the hydroxyl group was livelier at low temperature, while the activation rate of the hydrogen atom predicts on the contrary. The scanning electron microscope (SEM) and Raman spectra demonstrated that the introduction of CO₂ in the CH₄/H₂ atmosphere could reduce the deposition temperature and raise the deposition rate at low temperature.

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: The diamond coating can improve the performance and durability of cutting tool. To obtain the structure of nano/micro CVD diamond coating, the finite element analysis of nano/micro composite CVD diamond coating on boronized cemented carbide was carried on using ANSYS. The relationship between nanoand micron diamond layer thickness and coating fall off stress was simulated. The thickness of nanodiamond and the micron diamond layer was suggested for the nano/micro CVD diamond coating on boronized cemented carbide cutting tool.

Abstract: Bone drilling commonly exists in clinical practice and the heat and force generated by the drilling process has a huge impact on the surgery effect and the recovery of patients. High speed drilling, proved to have less injury and be more efficient when compared to the traditional low speed drilling, is considered to be the development direction of bone drilling-related surgeries. In order to make a further study of the controlling of the heat and force during the bone drilling process, the experiment designed to examine the influence of the diamond coating has been conducted and the result indicates that the diamond coating generally has little influence on the drilling force, however, it can increase the drilling temperature to a certain extent which indicates that the diamond coating is not suitable to apply to bone drills under the conditions of the conducted experiments. The result of this research could be of some help to the development of new kinds of medical drills.

Abstract: The present study reports the influence of graphene layers on the tribological performance of CVD diamond films when they are used as the solid lubricants. Friction tests are conducted on a ball-on-plate friction tester, where the stainless steel is used as the counterpart material. The CVD diamond film sample is a typical microcrystalline diamond (MCD) coating which is deposited on a flat tungsten carbide substrate using the hot filament chemical vapor deposition method (HFCVD). Besides the MCD sample, a polished MCD film (pMCD) and a polished tungsten carbide (pWC) are also adopted in frictional tests, aiming at illustrating the influence of the surface morphology, as well as the physical property, of the sample on the lubricative effect of graphene layers. The experimental results show that graphene layers can effectively reduce the coefficient of friction (COF), regardless of the samples. The MCD sample presents the lowest stable COF, which is 0.13, in dry sliding period when the graphene flakes are sparyed on the sliding interface; while the pMCD and pWC samples exhibit slightly higher COFs, which are 0.16 and 0.18, respectively. Comparatively, the COFs of these three samples obtained in dry sliding process without graphene are 0.20, 0.25 and 0.64. In additon, the MCD sample exhibits a much longer stable dry slidng process which is more than 5000 cycles. Comparatively, the other two tribo-pairs only exhibit a stable low-COF dry sliding period for around 2000 cycles. The reduction of COF could be attributed to the graphene flakes adhered on the sliding interface. It forms a layer of solid lubricative film with extremely low shear strength and significantly decreases the interactions between two contacted surfaces. The rugged surface of the MCD film provides sufficient clogging locations for graphene flakes, which allows the generated lubricative film enduring a long sliding duration. It can be arrived from this study that the tribological properties of the MCD film could be enhanced by simply adoping graphene layers as a solid lubricant. Furthermore, an improved performance of a variety of MCD coated cutting tools or mechanical components could be expected when they are utilized with graphene layers.

Abstract: The carbide cemented special drills with TiAlCrN/TiSiN coating and diamond coating respectively were selected to drilling on carbon fiber reinforced plastics (CFRP) for a contrast test in this paper. The drilling force , drilling exit surface quality and tool wear were analyzed separately to research the performance characteristics of the two kinds of special drills with different coating. The results show that: under the same cutting conditions, the thrust force of the special drill with diamond coating is smaller than that of the TiAlCrN/TiSiN coating, and the tool life is extended by 2 times at the same time. The diamond coated special drill can improve the drilling surface quality, it is more suitable for drilling CFRP.

Abstract: Carbon Fiber Reinforced Plastic (CFRP) is widely used in aerospace field as an advanced composite material. Recently, more and more studies are focused on milling of CFRP with its increasing applications. In this paper, three different milling tools were chosen, and a systematic analysis on cutting force, surface quality and tool wear has been carried out to evaluate the tools. Experimental results indicate that the multi-flute tool with diamond coating has a better performance than the double spiral compression tool and the multi-tooth tool with AlTiN coating, with a lower cutting force, a better surface quality and a higher tool life than others, which would be a better tool for cutting of CFRP.

Abstract: The diamond coatings were prepared by hot filament chemical vapor deposition(HFCVD) on the mono-crystalline silicon substrates. The influence of the technical parameters such as methane volume ratio, substrate temperature and reaction pressure on the residual stress in the diamond coating was studied. The results showed that the residual stress in the coating was compressive stress in the range of parameters studied, and too high or too low substrate temperature, chamber pressure and methane volume ratio would all increase the residual compressive stress. This relationship can be explained by the influence of amorphous carbon content, vacancy density and grain size on the residual stress.