Tribological Properties Of Diamond-like Carbon Research Articles

PVD coatings on punches for low interfacial adhesion to pharmaceuticals

The modification of the surface chemistry of steels is a crucial way to optimize different industrial processes, whether low or high adhesion is needed. In the case of compression of pharmaceuticals for tablet production, punches must have non-sticking properties to inhibit pharmaceutical adhesion. For this kind of application, it is necessary to develop hard coatings with low surface energy and static friction. For this aim, we investigated the physical, chemical, structural, mechanical, and tribological properties of diamond-like carbon (DLC) and transition metal dichalcogenides (TMD - WSC and WS2) coatings. In addition, we analyzed the potential of these coatings for pharmaceutical tablet fabrication. The coatings' surface free energy (SFE) was lower than that of blank steel, indicating better anti-adherent properties. The friction and morphology analysis showed that the tablets have less adhesion when in contact with selected coatings contrasting with higher adhesion in the uncoated sample. WSC was the coating showing the lowest adhesion for the four formulations studied in detail (paracetamol, fluvoxamine maleate, ibuprofen, and fertilizer). The results show that WSC is a suitable coating for the punches to produce tablets.

Tribological Properties of Diamond-Like Carbon, TiAlN, and Diamond-Like Carbon/TiAlN Coatings Deposited on Carburized 18CrNi4A Steel for Heavy-Duty Aerospace Transmission Components

Tribological Properties of Diamond-Like Carbon, TiAlN, and Diamond-Like Carbon/TiAlN Coatings Deposited on Carburized 18CrNi4A Steel for Heavy-Duty Aerospace Transmission Components

Improvement of the mechanical and tribological behaviors by Ti-C interlayer for diamond-like carbon films on nitrile butadiene rubber

To improve the mechanical and tribological properties of diamond-like carbon (DLC) film on nitrile butadiene rubber, the DLC/Ti-C bilayer films are fabricated by a dual-target magnetron sputtering method. The morphological characterization results indicate that the roughness of DLC/Ti-C first decreases and then increases slightly with the increase of Ti content and surface roughness of all modified samples is lower than that of nitrile butadiene rubber (NBR). Raman spectra show that the change of Ti content in the Ti-C interlayer has no effect on the ratio of sp2 to sp3 bonds of surface DLC film. The nanoindentation results show that the Ti content significantly affects the hardness, Young’s modulus, hrex/hmax and elastic recovery (%). Notably, the DLC/Ti-C films with a Ti content of 12.32 ∼ 14.77 at. % show the lowest coefficient of friction (CoF, 0.1 ∼ 0.2) and superior wear resistance due to the increased transformation of sp2 into sp3 in the films. This study unravels that the DLC films' superior mechanical and tribologic performance could be realized by regulating the Ti content in the Ti-C interlayer.

Effect of deposition temperature on the microstructure and tribological properties of Si-DLC coatings prepared by PECVD

The tribological properties of diamond-like carbon (DLC) coatings were influenced by their microstructure, which was controlled by the preparation technology and parameters. In this study, Si-DLC coatings were prepared on cemented carbide (YG10C) and stainless steel (316L) substrates by plasma enhanced chemical vapor deposition with various deposition temperatures. The effect of the deposition temperature on the microstructure and tribological properties was systematically investigated. The results showed that the sp3/sp2 values and hardness of the Si-DLC coatings increased firstly and then decreased as the deposition temperature increased from 60 °C to 180 °C, while the tendency in toughness, adhesion strength and residual stress is not consistent with it. The performance of the coatings obtained at 120 °C was best, while the coatings obtained at 150 °C had the lowest toughness due to the volume expansion caused by the transformation of sp3 to sp2. A graphite transfer layer was observed on the wear tracks of friction pairs. Thereinto, O-Si-C on the transfer layer could further reducing shear resistance and plays a role as a lubricant. Therefore, the coating prepared at the preferred deposition temperature had excellent tribological properties.

Improvement the tribological properties of diamond-like carbon film via Mo doping in diesel condition

To improve the tribological properties of diamond-like carbon (DLC) film in diesel engines, Molybdenum-doped DLC (Mo-DLC) film was prepared by a radio frequency (RF) magnetron sputtering system. The results showed that Mo content in the film was approximately 11 at.%. Mo doping decreased the internal stress of the DLC film and increased the adhesion of film-substrate from 40 mN to 190 mN. The sp2 bond content in the Mo-DLC film was increased and molybdenum carbide was formed by Mo doping, which led to the formation of nano-cluster/amorphous microstructure. The wear resistance of the Mo-DLC film was significantly improved under air and diesel conditions. The results of this study provide a better understanding of the tribology behaviour of the DLC films in air and diesel environment.

Effect of normal loads and mating pairs on the tribological properties of diamond-like carbon film

The influence of normal loads and mating pairs on the tribological properties of diamond-like carbon (DLC) film was investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman characterizations. The friction and wear behaviors of DLC film are not only related to the friction pairs but also related to the normal loads. The friction coefficient and wear rate of DLC film are smaller with the increase of load, but the wear degree of DLC film is more serious with the increase of hardness of the friction pair. Raman analysis indicates that the structural evolution of DLC film should have a limited contribution on the different friction behaviors of DLC film against ZrO2, bearing steel and SiC balls. The results of TEM and Raman characterizations further show that the key factor determining the low friction of DLC film is the graphitization degree of the transfer layer rather than the formation continuity and compactness of the transfer layer. The results further deepen our understanding of the related mechanisms between DLC films and friction pairs under different normal loads as guidance for the application of DLC films in future industrial fields.

High-temperature tribological properties of diamond-like carbon films: A review

Abstract The rapid development of aerospace industry has made more and more machinery parts of equipment working at high temperature. Due to the lubrication failure of lubricating oil and grease at high temperature, solid lubricant coatings are almost the only effective method to achieve super low friction at high temperature. In recent years, the tribological properties of diamond-like carbon (DLC) films have been extensively studied at high temperature. The present study reviews the microstructure of DLC films and the influence of doping different elements on the structure of DLC films. Second, the mechanical properties and thermal stability of pure DLC films and DLC doped with different elements are also described. DLC films have different microstructures and tribological properties by different preparation methods. Finally, the high-temperature lubrication failure mechanism of DLC films and the tribological properties of DLC films when doped with different elements are discussed from the macro and micro perspectives.

Effect of temperature and mating pair on tribological properties of DLC and GLC coatings under high pressure lubricated by MoDTC and ZDDP

Diamond-like carbon (DLC) and graphite-like carbon (GLC) coatings have good prospects for improving the surface properties of engine parts. However, further understanding is needed on the effect of working conditions on tribological behaviors. In this study, GLC and two types of DLC coatings were deposited on GCr15 substrate for investigation. The friction and wear properties of self-mated and steel-mated pairs were evaluated. Two temperatures (25 and 90 °C), three lubrication conditions (base oil, molybdenum dithiocarbamate (MoDTC)-containing oil, MoDTC+zinc dialkyldithiophosphate (ZDDP)-containing oil), and high Hertz contact stress (2.41 GPa) were applied in the experiments. The results showed that high temperature promoted the effect of ZDDP on steel-mated pairs, but increased wear under base oil lubrication. The increased wear for steel-mated pairs lubricated by MoDTC-containing oil was due to abrasive wear probably caused by MoO3 and β-FeMoO4. It was also found that in most cases, the tribological properties of self-mated pairs were better than those of steel-mated pairs.

Influence of currents on tribological behavior of diamond-like carbon films

The diamond-like carbon (DLC) film is vastly applied for low-friction protective films at contact sliding surfaces. This work reported the characteristics and tribological properties of DLC, Cu-doped DLC (Cu-DLC) film and Ti-doped DLC (Ti-DLC) film formed by unbalanced magnetron sputtering system and analyzed the frictional tests and the morphology of wear scars. The current intensity at the sliding interface was set to a constant value in the whole current circuit for exploring the influence of current, including 0 A, 0.5 A, 1 A, 1.5 A and 2 A. The results showed the friction coefficient of DLC film decreased from 0.12 to 0.06–0.08 and then increases rapidly to 0.26 when the current increased to 2 A. The change in trend of friction coefficient of Cu-DLC film with the increase in current was the same with the DLC film. The minimum value was 0.12 at 1 A current. In the case of Ti-DLC film, when the current intensity enhanced from 0 to 2 A, the friction coefficient monotonically increased from 0.06 to 0.29. Furthermore, the wear rate of the films under higher current was larger than the wear rate of the films under lower current. This is due to the fact that frictional heat and Joule heat are generated at a relatively large current to make the surface of the film more susceptible to wear. The wear rate of Ti-DLC film is relatively larger as the arc ablation is the main wear mechanism of Ti-DLC film compared with pure DLC film and Cu-DLC film.

Plasma preparation method and tribological properties of diamond-like carbon coating on magnesium alloy AZ31 substrate

Magnesium alloys are light weight and exhibit good recyclability but suffer from low hardness and wear resistance. In this study, the hardness and wear resistance of AZ31 magnesium alloy were improved by depositing diamond-like carbon (DLC) films as hard protective coatings using ion-beam-enhanced deposition with various CH4/H2 ratio, gas flow rates and accelerating voltages. The supporting effect of the magnesium alloy was enhanced by the production of a graded interfacial layer which is composed of film atoms and substrate atoms. The composition and mechanical properties of the DLC coatings were characterized using scanning electron microscopy (SEM), Raman spectroscopy, Rockwell test and nano-indentor. The tribological properties of the coating were also investigated using a frictional surface microscope with an in situ observation system and friction force measurements. The DLC films were characterized by a lower intensity ratio of the D-peak to G-peak (ID/IG), higher hardness, and improved tribological properties when deposited at a lower accelerating voltage (6 kV). At the CH4/H2 ratio of 1:99 and 6 sccm/6 kV, minimum ID/IG values of 0.62, relatively low friction force value of 0.12 N, and a maximum hardness of 4056HV were attained respectively. In addition, the DLC film exhibited improved wear resistance and a shallower wear track at this condition.

Effect of substrates on tribological properties of diamond-like carbon coating

Effect of substrates on tribological properties of diamond-like carbon coating

Ultralow Friction of a Tetrahedral Amorphous Carbon Film Lubricated with an Environmentally Friendly Ester-Based Oil

The tribological properties of diamond-like carbon (DLC) films that were lubricated with an environmentally friendly ester-based oil were investigated. Sliding tests were performed on two types of DLC films, hydrogenated amorphous carbon (a-C:H) and tetrahedral amorphous carbon (ta-C) films, using a steel cylinder that was in contact with a steel disk coated with either a-C:H or ta-C under boundary lubrication. To compare the tribological properties of ester-based oils and other based oils, Trimethylolpropane (TMP) ester, polypropylene glycol (PPG), and poly-alpha olefin (PAO) were used as the test lubricants. The ta-C film that was lubricated with TMP ester exhibited the ultralow friction coefficient of 0.015; however, the a-C:H film that was lubricated with TMP ester did not exhibit the ultralow friction. On the other hand, results obtained by a quartz-crystal microbalance with dissipation indicated that the adsorption properties of based oils depended on the type of sensor material (carbon or iron) and the type of based oil used in the measurements. Moreover, the frequency change of based oils increased with decreases in the average frictional coefficients of the steel-steel tribopair and the DLC-steel tribopair. Results of surface analysis indicated that TMP ester formed tribofilms on the ta-C surfaces, which exhibited high viscosity and low friction. All these results suggest that the combination of the ta-C film and TMP ester is the new ultra-low-friction and environmentally friendly sliding system.

Thickness Effects of TiC Interlayer on Tribological Properties of Diamond-Like Carbon Prepared by Unbalanced Magnetron Sputtering Method.

We investigated the tribological properties of diamond-like carbon (DLC) films prepared with TiC interlayer of various thicknesses as the adhesive layer. DLC and TiC thin films were prepared using unbalanced magnetron (UBM) sputtering method using graphite and titanium as targets. TiC films as the interlayer were deposited under DLC films and various physical, tribological, and structural properties of the films fabricated with various TiC interlayer thicknesses were investigated. With various TiC interlayer thicknesses under DLC films, the tribological properties of films were improved with increasing thickness and the DLC/TiC layer fabricated by unbalanced magnetron sputtering method are exhibited maximum high hardness over 27 GPa and high elastic modulus over 242 GPa, and a smooth surface below 0.09 nm.

Durability of ZDDP Tribofilms Formed in DLC/DLC Contacts

The tribological properties of diamond-like carbon (DLC) coatings have drawn much attention of OEMs and lubricant manufacturers in recent years. It is important to know whether conventional friction modifier and antiwear additives can form durable films and work as effectively with DLCs as they normally do on steel surfaces. In this study, the film-forming and friction properties of the antiwear additive ZDDP and the strength of tribofilms formed by this additive on five widely used DLC types, namely a-C:H, a-C:H:W, a-C:H:WC, Si-DLC and ta-C, have been investigated. It is found that ZDDP-derived tribofilms form on all the DLCs but exhibit different friction characteristics based on DLC type. With all DLCs, the amount of tribofilm elements measured after durability tests was less than that measured initially. Over 90 % of thiophosphate and 70 % of sulphide/sulphate were lost during durability tests. ZDDP tribofilms were found to be strongly adhered on Si-DLC and a-C:H compared with the other DLCs. The ZDDP tribofilms formed in DLC/DLC contact appear to be similar in structure to those formed in steel/steel contact but not to exhibit the antiwear performance seen in steel/steel contacts.

Tribological Properties of DLC Films Deposited at Different Time under Low Temperature

The tribological properties of DLC(Diamond like carbon) films deposited for different time on mono-crystalline silicon were investigated by using the UMT-2 micro friction and wear tester. The surface topography, composition and hardness of the films were determined by three-dimensional topography instrument, Raman spectrum and nano mechanics tester. The worn surface topography of the films deposited for different time were observed by scanning electron microscopy. The results show that the thickness of the films deposited for different time is nonlinearly increased with the deposition time. The films are the standard nano-films. The surface hardness of the films is low because the films contain hydrogen composition and the deposition temperature is very low. The films deposited for different time have a good anti-friction property, which is improved when the deposition time is prolonged.

Influence of high temperature annealing on the structure, hardness and tribological properties of diamond-like carbon and TiAlSiCN nanocomposite coatings

Diamond-like carbon (DLC) and TiAlSiCN nanocomposite coatings were synthesized and annealed at different temperatures in a vacuum environment. The microstructure, hardness and tribological properties of as-deposited and annealed DLC–TiAlSiCN nanocomposite coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, nano-indentation and friction tests. The TEM results reveal that the as-deposited DLC–TiAlSiCN coating has a unique nanocomposite structure consisting of TiCN nanocrystals embedded in an amorphous matrix consisting of a-Si3N4, a-SiC, a-CN and DLC, and the structure changed little after annealing at 800°C. However, XPS and Raman results show that an obvious graphitization of the DLC phase occurred during the annealing process and it worsened with annealing temperature. Because of the graphitization, the hardness of the DLC–TiAlSiCN coating after annealing at 800°C decreased from 45 to 36GPa. In addition, the DLC–TiAlSiCN coating after annealing at 800°C has a similar friction coefficient to the as-deposited coating.

Microstructure and tribological properties of diamond-like carbon and TiAlSiCN nanocomposite coatings

Diamond-like carbon (DLC) and TiAlSiCN nanocomposite coatings were synthesized by multi-plasma immersion ion implantation and deposition. The DLC content in the composite coating was controlled by the flow ratio of N 2 to C 2H 2 during the deposition process. The microstructure and tribological properties of the as-deposited coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), nanoindentation and ball-on-disk friction tests. The TEM results show that all the DLC-TiAlSiCN coatings had a two phase composite structure of the TiCN nanocrystals embedded in an amorphous matrix consisting of a-Si 3N 4, a-SiC, a-CN and DLC. TEM observations also reveal that the spacing between the adjacent nanocrystals increases with DLC content. In addition, the DLC-TiAlSiCN nanocomposite coating with a small crystalline spacing of about 0.6 nm shows a higher hardness up to 50 GPa and a larger friction coefficient. An increase in the DLC content of the coating benefits its friction coefficient while its hardness decreases. The friction coefficient reduces to 0.14 when the DLC content is about 31%.

ChemInform Abstract: Temperature and Bias Effects on the Physical and Tribological Properties of Diamond-Like Carbon.

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508 ダイヤモンドライクカーボン膜のトライボロジー特性に及ぼす紫外線照射の影響(OS7-2 最先端および環境対応加工技術2,OS7 最先端および環境対応加工技術)

508 ダイヤモンドライクカーボン膜のトライボロジー特性に及ぼす紫外線照射の影響(OS7-2 最先端および環境対応加工技術2,OS7 最先端および環境対応加工技術)

Effects of water environment on tribological properties of DLC rubbed against brass

The effects of the water environment, such as temperature, dissolved ions, and dissolved oxygen, on the tribological properties of diamond-like carbon (DLC) against brass were studied as part of the development of water-lubricated hydraulics, valves and cylinders based on metals (Fe alloys, Cu alloys, etc.). A ball-on-disk type tribotester was used to examine the above various factors. DLC was deposited on stainless steel disks using an unbalanced magnetron sputtering system. Pure water and quasi-tap water, which imitate typical tap water sampled in Tokyo, were used to study the effects of dissolved ions. The water temperature was elevated from 20°C to 80°C. The results show that temperature as well as the dissolved ions has a major impact on friction and wear. More specifically, the coefficient of friction was increased at elevated temperatures. Also, in pure water, abrasive wear of DLC was observed due to aluminum condensation on the brass surface, whereas it was prevented in quasi-tap water since aluminum was removed from the contact region due to the dissolved ions. EPMA, XPS and AES indicated that the tribo-layer on the metal surfaces, which consists of carbon and the base metal as well as some elements from water, plays an important role.