Wear Of DLC Research Articles

Comparison of TiAlN DLC and PCD Tool Wear in CFRP Drilling

Comparison of TiAlN DLC and PCD Tool Wear in CFRP Drilling

高温高圧水含有エタノール中におけるDLC膜の摩耗メカニズム

DLC coatings have been applied to many automotive parts. This is because they have excellent properties such as low friction, high hardness, high wear resistance and chemical stability. Recently, bioethanol fuel has been attracting attention as a carbon-neutral fuel. However, the wear characteristics of DLC coatings under high-temperature and high-pressure environments, such as automobile engine environments, have not yet been clarified. In this study, friction and wear tests were conducted on Si-containing DLC coatings in ethanol containing high-temperature, high-pressure water. After friction test, we performed elemental analysis by Auger electron spectroscopy and AFM nano-scratch testing of wear scar of DLC coatings. As a result, it was found that the Si content suppressed the wear of DLC as the ethanol concentration increased, that the wear increased due to the effect of water, and that the wear increased due to the removal of the soft layer formed on the wear scar surface.

Wear of hydrogenated DLC in MoDTC-containing oils

This paper describes a study of the effect on MoDTC-promoted a-C:H DLC wear of adding various surface-active additives used in engine lubricants, including ZDDP, an ashless EP additive, Ca detergents, dispersants, an OFM and a PAMA, to an MoDTC solution. Tribofilms formed on wear tracks on steel were analysed using SLIM, TEM, STEM-EDX, Raman spectroscopy and XPS. Relevant mechanisms by which these additives reduce the impact of MoDTC on DLC wear have also been suggested. DLC wear in PAO+Mo can be reduced by the presence of other surface-active additives in three ways. Firstly, asperity contact between DLC and steel can be mitigated by forming thick antiwear tribofilms. Secondly, other additives can increase the ratio of MoS2:MoO3, reducing the amount of wear-enhancing MoO3 in the tribofilm. Thirdly, the amount of MoDTC tribofilm including MoO3 can be reduced by the competitive adsorption of other surface-active additives. This study has practical implications for ways in which DLC surfaces can be protected by lubricant formulation.

Tribo-Raman-SLIM observation for diamond-like carbon lubricated with fully formulated oils with different wear levels at DLC/steel contacts

Tribological phenomena of DLC–steel tribo-systems in fully formulated oils were investigated using a Tribo-Raman-spacer layer imaging method (SLIM), which can evaluate the tribological behavior, tribofilm formation process, and tribofilm thickness on the sliding surface. In particular, the effects of the formation process of the tribofilm on the steel surface on the wear phenomena of the DLC were investigated using oil formulations with three different wear levels as test lubricants. The oils were labeled based on the wear results of an engine wear test conducted on the DLC coated-tappet at the DLC coated-tappet/steel-cam contacts. A friction test was conducted at the hydrogenated amorphous carbon DLC (a-C:H DLC) disk/steel ball contacts lubricated with the three formulated oils. The in-situ Raman-SLIM results revealed that thicker phosphate tribofilms with a large number of P–O–P bridges led to lower wear volume of DLC. In other words, the growth of the phosphate tribofilm is a key factor inhibiting the Mo-FMs-induced wear of DLC. Therefore, a booster that can contribute to the growth of the phosphate tribofilms on the steel surface is effective in inhibiting the wear of DLC under the lubrication with fully formulated oils.

The Application of DLC Coating on Convex-concave (C-C) Gearings

This paper discusses the possibility of increasing the surface load capacity in C60E steel gearings by applying DLC thin coating. It describes the effect of tribological characteristics, such as friction coefficient, wear, adhesion and hardness of DLC coating on convex-concave gearing (C-C). The average thickness of DLC coating is 1.2 μm. Delamination of the DLC coating was recorded at a load of approximately 50 N. The friction coefficient of the DLC coating was 0.09. The nano-hardness of the DLC coating was 14.4 GPa. The results of the tests to scuffing on C-C gearings on the Niemann tester show that the DLC coating deposition occurred at load level 5. The complete removal of the coating was preceded by gradual thinning. After its removal, the wear continued substrate, where the traces after milling filled-up with the substrate metal.

Real-time observation of slipping and rolling events in DLC wear nanoparticles

Real-time observation of the actual contact area between surface interfaces at the nanoscale enables more precise examination of what happens during friction. We have combined micro electro mechanical system actuators and transmission electron microscopy (TEM) observation, to both apply and measure forces across nanoscale junctions and contacts. This custom-designed experimental system can measure the true surface area of a contact site from a lateral viewpoint, while simultaneously measuring the friction force. We scratched surfaces coated with diamond like carbon, a classical solid lubricant, and observed the formation of wear particles that slipped and rolled between the interface. TEM images showed that the shape of the surface at the nanoscale underwent permanent deformation when acted upon with forces as low as several tens of nano newtons. The results demonstrated the limitations of friction analyses relying on friction force measurements without real-time surface profiling.

Formation of interfacial molybdenum carbide for DLC lubricated by MoDTC: Origin of wear mechanism

A large amount of research has been devoted to the effect of molybdenum dithiocarbamate (MoDTC) additives on the lubricating performances of carbon-based coatings, showing that a high wear rate is produced when the MoDTC is blended with the base oil. However, the mechanisms leading to the coating removal are not fully understood yet.In this work, the friction and wear performances of an amorphous hydrogenated DLC coating doped with silicon and oxygen have been analysed when lubricated by MoDTC-containing oils. Tribological experiments have been conducted with DLC/steel and DLC/DLC contacts under boundary lubrication conditions using a ball-on-flat tribometer. To understand the wear mechanism, the chemical composition of the tribofilm formed on the steel ball counterpart was investigated by X-ray Photoelectron Spectroscopy (XPS). Transmission Electron Microscopy (TEM) coupled with Energy Dispersive X-Ray Spectroscopy (EDX). A new DLC wear model has been proposed and validated.

DLC 膜の潤滑油中摩耗に及ぼす三酸化モリブデンの影響

DLC 膜の潤滑油中摩耗に及ぼす三酸化モリブデンの影響

Tribological behaviour analysis of hydrogenated and nonhydrogenated DLC lubricated by oils with and without additives

ABSTRACTDiamond‐like carbon (DLC) is an essential element of friction reduction made major by the desire to reduce energy consumption for environmental and economic reasons. The contribution of the DLC depends on its tribological behaviour. The analysis of the wear of DLC in DLC/steel contact is important because of the high exposure to the wear of coated parts and the low degree of mastery of behaviour of DLC in the lubricants studied and optimised for steel. In this study, we have analysed the tribological behaviour of hydrogenated DLC (a‐C:H) and nonhydrogenated DLC (ta‐C) under various lubrication conditions. Oils with and without additives were used. The results show that the wear of a‐C:H is considerably lower than that of ta‐C in base oils, and in the investigated oil with additives, the wear of ta‐C is substantially reduced. Copyright © 2012 John Wiley & Sons, Ltd.

Effect of DLC Film on Tribological Properties of Carbon/Carbon Composites

The effect of DLC film on tribological properties of C/C composites was investigated with a ball-on-disk tribometer in dry air, compared with the result of specimen without DLC film. The DLC film was prepared on the surface of C/C composites substrate by plasma enhanced chemical vapor deposition method (PECVD). After PECVD, structural characterization of the film, adhesion strength of film to substrate, surface morphology and linear wear were studied by Raman spectroscopy, Rockwell-C apparatus, Scanning Electron Microscopy (SEM) and Optical Microscopy (OM), respectively. The result showed that the film deposited on the surface of C/C substrate exhibited typical Raman spectroscopy fingerprints of DLC films and a good adhesion to the substrate surface was found. A stable friction coefficient was observed during the friction tests. With the DLC film, the friction and wear properties of C/C composites were improved significantly. The average friction coefficient of the C/C specimen with DLC film (0.08637) was reduced by 65.56% than that of the one without DLC film (0.2508) and the linear wear was decreased by 84.7% ( from 148.47μm to 22.71 μm) as well.

Enhanced DLC wear performance by the presence of lubricant additives

Lubricant additives play significant role for reducing friction and wear of mechanical elements. The additives presented in 5W30 oil were developed for metal surfaces. However, they have been used in engine pieces covered with DLC coatings because they also offer the potential to reduce friction losses and wear in automotive applications. The friction and wear tests were carried out by using a UMT-CETR ball-on-disk tribometer in rotational mode under 5W30 synthetic oil at 100 °C. The X-ray photoelectron spectroscopy (XPS) showed the presence of Mo and S in the wear tracks. These elements are from decomposition of ZDDP and MoDTC additives producing MoS2 in DLC surface, which offers enhanced durability by low wear rate.

Effect of Friction Modifiers and Antiwear Additives on the Tribological Performance of a Hydrogenated DLC Coating

There has been a lot of attention on the effect of lubricant additives on the friction at carbon coated surfaces. But only few papers have addressed the effect of additives on the durability of some diamondlike carbon DLC coatings. This paper presents a systematic study assessing the additive/additive and additive/surface interactions, and their influences on the durability of a low hydrogen-containing (15 at. % hydrogen) metal-free DLC coating (a-C:15H). In this study, lubricating oils containing a zinc dithiophosphate (ZDDP) antiwear additive and/or organomolybdenum friction modifiers (moly dimer and moly trimer) were used. Tribological tests were carried out in a pin-on-plate tribometer under boundary lubrication conditions. To understand the effect of additives, tribofilms formed on the wear tracks were analyzed using surface sensitive analytical techniques such as atomic force microscope, scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy. Results showed that the ZDDP formed a zinc phosphate containing an ultrathin antiwear tribofilm, which offered excellent durability/wear protection to the a-C:15H coating. However, the antiwear performance of this additive was compromised when it was used with moly dimer or moly trimer. Surface analysis revealed that unlike steel surfaces, MoS2 formed on the DLC surfaces had negligible influence on friction, while the low friction DLC wear debris had strong influence on friction. Abrasive wear was found to be the dominating wear mechanism in the cases when additives showed poor wear protection on the a-C:15H coating.

907 DLC膜の摩擦・摩耗特性評価のための一解析(機素潤滑設計II)

907 DLC膜の摩擦・摩耗特性評価のための一解析(機素潤滑設計II)

Tribochemical investigation of DLC coating tested against steel in water using a stable isotopic tracer

Tribochemical reaction of DLC coating in water was investigated using a stable isotopic tracer, heavy water (deuterium oxide, D 2O), in which the friction test of DLC coating and 440C ball pair was carried out. The worn surfaces were analyzed by ToF–SIMS. For comparison, a test was also conducted in ion exchanged water (H 2O). The result showed that tribochemical reaction between DLC and D 2O occurred, and CD, OD groups were formed on the worn DLC surface. It is suggested that OD groups mainly combine with the secondary or tertiary carbons on the surface. It is considered that the formed hydrophilic hydroxyl groups play an important role in reducing the friction and wear of DLC coating and the counter part in a water environment.

Effects of water environment on tribological properties of DLC rubbed against stainless steel

The effects of water environment on tribological properties of DLC against stainless steel were studied for development of the hydraulic pumps, valves and cylinders based on metal. A ball-on-disk tribotester was developed for detailed examination of water environment, such as temperature (20–80 °C), dissolved oxygen (0.01–8 ppm), water pressure (0.1–20 MPa) and dissolved ions. DLC was deposited on the disk by the unbalanced magnetron spattering system. Pure water and quasi-tap water were used to study the effects of dissolved ions. The results showed that temperature and dissolved ions have a major impact on friction and wear of DLC. EPMA, XPS and AES indicated that tribofilm on the metal surface, which consists mainly of C, O and Fe, plays important role for the phenomena.

Role of molybdenum carbide and titanium nitride in the sintering of materials containing titanium and chromium carbides: T. Hachisuka, J. Japan Soc. Powder and Powder Metallurgy, Vol 38, No 2, 1991, 145–152, (In Japanese)

A large amount of research has been devoted to the effect of molybdenum dithiocarbamate (MoDTC) additives on the lubricating performances of carbon-based coatings, showing that a high wear rate is produced when the MoDTC is blended with the base oil. However, the mechanisms leading to the coating removal are not fully understood yet.In this work, the friction and wear performances of an amorphous hydrogenated DLC coating doped with silicon and oxygen have been analysed when lubricated by MoDTC-containing oils. Tribological experiments have been conducted with DLC/steel and DLC/DLC contacts under boundary lubrication conditions using a ball-on-flat tribometer. To understand the wear mechanism, the chemical composition of the tribofilm formed on the steel ball counterpart was investigated by X-ray Photoelectron Spectroscopy (XPS). Transmission Electron Microscopy (TEM) coupled with Energy Dispersive X-Ray Spectroscopy (EDX). A new DLC wear model has been proposed and validated.