Diamond-like Carbon Coatings Research Articles

Остеоинтеграция имплантатов с алмазоподобным углеродным покрытием в условиях эксперимента

Цель. Изучить в эксперименте на крысах интеграцию с костью металлических имплантатов из нержавеющей стали с алмазоподобным углеродным (DLC) покрытием. Материал и методы. Эксперимент проведен на 48 белых крысах-самцах в возрасте 6 месяцев. Животным имплантировали в метафизарные дефекты бедренной кости (диаметр 2 мм и глубина 3 мм) имплантаты из стали и стальные имплантаты с DLC-покрытием (по 24 крысы в контрольной и опытной группах). На поверхность стального имплантата наносили DLC-покрытие из отфильтрованных потоков вакуумно-дуговой плазмы. Материал покрытия не содержал примесей металлов и водорода. Нанотвердость нанесенного на образец покрытия составляла от 30 до 40 ГПа. Толщина DLC-покрытия составляла не менее 1 мкм. Эвтаназию крыс проводили через 7, 14, 30 и 90 дней после операции путем введения летальной дозы тиопентала натрия (90 мг/кг внутримышечно). Ремоделирование кости вокруг имплантатов исследовали гистологическими методами с морфометрической оценкой остеоинтеграции (контакт костной ткани с имплантатом в процентах). Результаты. Алмазоподобное углеродное покрытие на стальных имплантатах обладает высокими адгезионными качествами, о чем свидетельствует прикрепление клеток к поверхности в течение 7 дней после имплантации и формирование вокруг них костной ткани через 14 дней. Вокруг стальных имплантатов зафиксировано образование прослойки из соединительной ткани с участками костной ткани. Выявлено, что за весь период исследования вокруг имплантатов из стали с DLC-покрытием процент остеоинтеграции был выше по сравнению с имплантатами без покрытия: на 14-й день – в 2,6 раза, на 30-й день – в 2,1 раза, на 90-й день – в 1,5 раза. Заключение. Алмазоподобные углеродные покрытия на стальных имплантатах являются перспективным материалом для использования в ортопедии и травматологии благодаря биосовместимости, остеоинтеграции и отсутствию негативного ремоделирования прилегающей костной ткани. Научная новизна статьи Впервые в эксперименте изучена перестройка кости вокруг имплантатов с разработанным алмазоподобным углеродным покрытием. Установлено, что использованное покрытие обладает биосовместимостью и высокими показателями остеоинтеграции.

Effect of Molybdenum Content on Mechanical and Tribological Properties of Diamond-Like Carbon Coatings over Titanium β-21S Alloy

Molybdenum-doped diamond-like carbon (Mo-DLC) coatings have been deposited on titanium β-21S alloy (Ti–15Mo–3Nb–3Al–0.2Si) using plasma-enhanced chemical vapor deposition (PECVD) equipped with pulsed-DC magnetron sputtering. Mo contents in the deposited coatings have been controlled with an applied sputtering pulse duty cycle. Chemical composition, structure, morphology, and topography have been studied using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM), respectively. XRD pattern of the coating with highest Mo content shows the presence of carbide phase. Smooth features with low roughness values are observed in low Mo content coating, whereas high Mo content coating shows granular characteristics with a high roughness value. Raman spectra reveal the increased graphitic content for the highest metal concentration in the coatings, wherein the nanohardness is also determined to be highest, at about ~18–19 GPa. Furthermore, the ball-on-disk tribometry test on Mo-DLC coating with highest nanohardness shows a low coefficient of friction (COF) of 0.2 with low wear loss compared to that of the substrate (0.62).

Electroless Deposition of Ni-P Coatings on HNBR for Low Friction Rubber Seals

This paper reports a simple and cost-effective procedure to coat hydrogenated nitrile butadiene rubber (HNBR) with a well-adherent Ni-P film by using the electroless plating method. A HNBR surface functionalization process was first optimized, creating an interpenetrating network with polyvinylpyrrolidone (PVP). Silver nanoparticles were deposited on PVP and acted as catalysts for the Ni-P film deposition, eliminating the expensive tin-palladium sensitization/activation step. A homogeneous, low phosphorous Ni-P film was obtained after 60–120 min of plating in an alkaline bath, with an average thickness of 3 to 10 µm, respectively. The PVP internetwork played an important role on the strong adhesion of the film, 1.0 ± 0.5 MPa. The tribological behavior of Ni-P-plated HNBR samples was studied for 1, 5 and 10 N applied loads under dry sliding on a pin-on-disc configuration and the coefficient of friction (CoF) was reduced by ~30–49%, compared to uncoated HNBR (loads 1–5N). Based on these results, Ni-P-coated rubber can be regarded as a novel solution for enhancement of the tribological behavior of dynamic seals; it can be regarded as a means to avoid machinery failure. This method offers an alternative to the diamond-like carbon (DLC) coatings.

Influence of Diamond-Like Carbon Coating on the Channel Deformation of Injection-Molded Microfluidic Chips during the Demolding Process.

Injection molding is one of the main techniques for manufacturing microfluidic chips. As an important stage, the demolding process in injection molding will directly affect the quality of the functional unit of microfluidic chips (polymer microchannels), thus limiting the realization of its functions. In this study, molecular dynamics (MD) simulations on the demolding process were carried out to investigate the influence of diamond-like carbon (DLC) coating on the channel deformation. The channel qualities of polystyrene (PS), polymethyl methacrylate (PMMA), cyclic olefin copolymer (COC) and polycarbonate (PC) were analyzed after demolding with nickel (Ni) and DLC-coated mold inserts, respectively. In particular, the non-bonded interfacial interaction energy, elastic recovery and gyration radius of polymer molecular chains were further studied. The results showed that the non-bonded interfacial interaction energies could be significantly reduced by DLC-coating treatment on the mold insert. Moreover, common channel defects such as molecular chain separation, surface burrs and necking did not occur. The treatment of DLC coating could also significantly reduce the change in the gyration radius of polymer molecular chains, so the morphology of the polymer channel could be maintained well. However, the change in the elastic recovery of the polymer channel was increased, and the opening width became larger. In a word, DLC-coating treatment on the mold insert has great application potential for improving the demolding quality of injection-molded microfluidic chips.

High temperature tribological behaviour of PVD coated tool steel and aluminium under dry and lubricated conditions

Aluminium alloys are commonly used as lightweight materials in the automotive industry. This non-ferrous family of metallic alloys offers a high versatility of properties and designs. To reduce weight and improve safety, high strength-to-weight ratio alloys (e.g. 6XXX and 7XXX), are increasingly implemented in vehicles. However, these alloys exhibit low formability and experience considerable springback during cold forming, and are therefore hot formed. During forming, severe adhesion (i.e. galling) of aluminium onto the die surface takes place. This phenomenon has a detrimental effect on the surface properties, geometrical tolerances of the formed parts and maintenance of the dies. The effect of surface engineering as well as lubricant chemistry on galling has not been sufficiently investigated. Diamond-like carbon (DLC) and CrN physical vapour deposition (PVD) coated steel have been studied to reduce aluminium transfer. However, the interaction between lubricants and PVD coatings during hot forming of aluminium alloys is not yet fully understood. The present study thus aims to characterise the high temperature tribological behaviour of selected PVD coatings and lubricants during sliding against aluminium alloy. The objectives are to first select promising lubricant-coating combinations and then to study their tribological response in a high-temperature reciprocating friction and wear tester. Dry and lubricated tests were carried out at 300 °C using a commercial polymer lubricant. Tests using DLC, CrN, CrTiN, and CrAlN coated tool steel were compared to uncoated tool steel reference tests. The initial and worn test specimen surfaces were analysed with a 3-dimensional (3D) optical profiler, scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDS) as to understand the wear mechanisms. The results showed formation of tribolayers in the contact zone, reducing both friction and wear. The stability of these layers highly depends on both the coatings’ roughness and chemical affinity towards aluminium. The DLC and CrN coatings combined with the polymer lubricant were the most effective in reducing aluminium transfer.

Effect of nitrogen (N2) flow rate over the tribological, structural and mechanical properties diamond-like carbon (DLC) thin film

In this article, nitrogen (N2) doped diamond-like carbon (N-DLC) coatings are deposited by Atmospheric pressure chemical vapor deposition (APCVD) technique at varying N2 flow rates and are investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, nanoindentation (NI) and nano scratch (NS) characterization. The wear rate (WR) and coefficient of friction (μ) of the N-DLC thin films increase from 1.32 × 10−4 to 3.11 × 10−4 μm2 and 0.05 to 0.15 with the increase of load from 40 to 70 mN at 70 sccm N2 flow rate. The results showed that there is a significant improvement in the tribological and mechanical properties of the APCVD synthesized DLC film as compare to the other PVD deposited DLC film.

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.

Exploring long-run reciprocating Wear of diamond-like carbon coatings: microstructural, morphological and tribological evolution

Diamond-like carbon (DLC) coatings were deposited on SUS304 and YT15 substrates by an ionic enhanced physical vapour deposition device with the unbalanced magnetron sputtering. An AlTiN transition layer was selected to be deposited on half of the samples. The microstructure, roughness, hardness, toughness, adhesive properties and tribological behaviour were systematically evaluated to explore the coating surface evolution in the long-run reciprocating wear. Results indicate that the high hardness substrate can improve the wear behaviour of the coating at the early stage of abrasion. The dispersed contact stress can lead to a decrease in the transformation tendency of the sp3 structure to the graphite-like sp2 structure. Moreover, the ID/IG ratio of the DLC coatings deposited on different combinations of the substrates and AlTiN transition layer tends to stabilise as the abrasion times exceeded 100,000 cycles. The present results help to promote the scientific understanding and engineering application of DLC films in long-run reciprocating wear.

Synthesis and Ex-Situ characterizations of diamond-like carbon coatings for metallic bipolar plates in PEM fuel cells

Metallic bipolar plates can significantly increase the power density of polymer electrolyte membrane fuel cells; however, they require corrosion-protection coatings with desirable physical and chemical properties. In this study, diamond-like carbon (DLC) film coatings are investigated as such coatings potentially for metallic-based bipolar plates, with the focus on the relation between the processes and properties of the coatings under different coating deposition conditions of Plasma Enhanced Chemical Vapor Depsoition (PECVD) method. Various characterization techniques are applied to study the adhesion, structure, morphology, wettability, corrosion, and electrical resistivity of the film coatings. XPS, EDAX, and SEM analyses are used to identify the ratio of sp3 (diamond-like) and sp2 (graphite-like) bonds in the coatings, surface elements, and surface morphology, respectively. Potentiodynamic polarization test is utilized to investigate the corrosion behaviors of substrates with and without DLC coatings. Further, the electrical resistivity of the DLC films is measured by the four-point probe method. The results indicate that higher deposition power along with the absence of argon gas results in more sp3 than sp2 bonds in the coating, and the electrical resistivity is increased accordingly. The coating films deposited from methane (CH4) exhibit superior adhesion to the stainless steel (SS316) substrates over those generated from acetylene (C2H2) gas. Coating films deposited on the metallic substrates change the surface wettability appreciably. Further, polarization tests show that coatings generated with a low power of 250 W and higher argon gas percentage of 30% provide better anti-corrosion protection for metallic-based bipolar plates.

Diamond-like carbon coatings alloyed with chromium – nanocomposite structure and tribological behavior in conditions of dry and boundary lubricated friction

The results have been presented of the vacuum deposited diamond-like carbon (DLC) coatings alloyed with chromium investigation devoted to elucidate the mechanisms of their friction and wear in the conditions of unlubricated and partially lubricated tribological contact. It has been demonstrated that in these coatings the features of their micro- and nanocomposite structure formed by the nanosized inclusions of metallic chromium and its interstitials in the DLC matrix have a significant influence on the tribological behavior under dry friction. In the case of a boundary lubricated contact the common practice is to associate the main role of alloying elements with the peculiarities of their tribochemical interaction with the chemically active components of the lubricant. However the present investigation has not confirmed the existence of such a synergistic effect of to tribochemical interaction of alloying metal and chemically active lubricant additives for the coatings obtained via magnetron sputtering of chromium in acetylene-based reactive atmosphere.

Effects of Varying Power and Argon Gas Flux on Tribological Properties and High-Speed Drilling Performance of Diamond-Like Carbon Coatings Deposited using High-Power Impulse Magnetron Sputtering System

This study examines the effects of different pulse powers and gas fluxes on the mechanical and tribological properties and high-speed drilling performance of diamond-like carbon coatings deposited on tungsten carbide substrates by high-power impulse magnetron sputtering. It is shown that an appropriate pulse power is essential in improving the mechanical and tribological properties of the coatings. Specifically, coatings deposited with a pulse power of 5 kW possess a high hardness and good tribological properties, as evidenced by a high hardness-to-elastic modulus ratio. The optimal deposition parameters are determined to be a pulse power of 5 kW and an argon flux of 80 sccm. The resulting coating (designated as C80/5) has the highest hardness (24.95 GPa) of the various coatings and wear rates 11.1, 7.3 and 6.2 times better than those of the bare WC substrate under loads of 6 N, 10 N and 14 N, respectively. Moreover, the coating has low coefficient of friction values of 0.086, 0.098 and 0.062 under loads of 6 N, 10 N and 14 N, respectively. The micro-drilling tests show that the drill coated with C80/5 has a lifetime three times longer than that of an uncoated micro-drill.

Effect of Diamond-Like Carbon Coating on Preventing the Ingress of Hydrogen into Bearing Steel

The failure of moving mechanical components is often accompanied by hydrogen embrittlement caused by hydrogen diffusion in steel. One considerable mechanism for hydrogen diffusion is its ingress from lubricant decomposition. We quantitatively investigated the ingress of hydrogen generated by lubricant decomposition into bearing steels using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Deuterated lubricants were used to discriminate between the original hydrogen in steel and the hydrogen generated from lubricant decomposition. The highest concentration of deuterium was always near the raceway surface, and the concentration decreased gradually as the depth was increased. The diffused deuterium increased in a parabolic relation with the duration of friction. To protect steels against the ingress of hydrogen, we studied the effect of a diamond-like carbon (DLC) coating, which has a low diffusion coefficient of hydrogen. DLC reduced but did not completely prevent the ingress of hydrogen, which resulted from the reduction in the amount of hydrogen generated from the tribochemical and thermal decomposition of lubricants.

Recent progress in materials used towards corrosion protection of Mg and its alloys

Magnesium has little resistance to corrosion and therefore its production and use are quite limited. The problem of corrosion associated with these alloys has been alleviated to some extent by the advantages obtained from fine coatings. An additional dense barrier against corrosion is created, using coatings obtained from sol-gel. As an alternative for Cr-based conversion coatings, rare-earth elements-based ones are been increasingly investigated for Mg and its alloys due to being eco-friendly. Because of chemical inertness, low friction, and high hardness, diamond-like carbon (DLC) coatings have exhibited the best protection for Mg and its alloys. In this review, we shed light on recent advancements in novel coatings for Mg alloys including hybrid, rare-earth conversion, composite polymeric (polymer composite is a multi-phase material in which reinforcing fillers are integrated with a polymer matrix), and DLC coatings. &nbsp

Additional Tribological Effect of Laser Surface Texturing and Diamond-Like Carbon Coating for Medium Carbon Steel at Near Room Temperature

Texture surface containing both micro-pits and a thin carbon coating was produced using laser surface texturing and magnetic-control vacuum sputtering. Tribological properties of the laser-textured surface coated with thin carbon were experimentally investigated at low-temperature (8–10 °C) under starved and lubricated conditions with a ring-on-ring test rig. The results indicated that the laser-textured surface combined with carbon coating (textured + coating) exhibited low wear intensity and friction coefficient under lubricated conditions, while moderate wear was observed under starved lubrication conditions as compared with the smooth, textured, and carbon-coated surfaces. The wear mechanisms of the lubricated, textured, coated surface under three working conditions (10 N and 1.25 m/s, 16 N and 0.25 m/s, and 50 N and 0.05 m/s) revealed plowing effect, corrosion, and adhesive wear, while oxidative and adhesive wears were observed under starved lubrication. Finally, the textured, coated surface was freely adaptable to different working conditions and exhibited additional effects for better tribological applications at low-temperature as compared with the smooth, laser-textured, and carbon-coated surfaces.

New strategy for reducing the EHL friction in steel contacts using additive-formed oleophobic boundary films

In this study we present a mechanism for the elastohydrodynamic (EHD) friction reduction in steel/steel contacts, which occurs due to the formation of oleophobic surface boundary layers from common boundary-lubrication additives. Several simple organic additives (amine, alcohol, amide, and fatty acid) with different molecular structures were employed as the model additives. It was found that the stronger chemisorption at 100 °C, rather than the physisorption at 25 °C, is more effective in friction reduction, which reaches 22%. What is more, EHD friction reduction was obtained in steel/steel contacts without use of the diamond-like carbon (DLC) coatings with their wetting or thermal effect, which was previously suggested as possible EHD friction reduction mechanism; yet about the same friction reduction of about 20% was obtained here—but with much simpler and less expensive technology, namely with the adsorbed oleophobic surface layers. A small variation in the additive’s molecular structure results in significant changes to the friction, indicating good potential in future EHD lubrication technology, where these additives could be designed and well optimised for notable reduction of the friction losses in the EHD regime.

Ab initio insights into the interaction mechanisms between boron, nitrogen and oxygen doped diamond surfaces and water molecules

Diamond and diamond-like carbon coatings are used in many applications ranging from biomedicine to tribology. A wide range of dopants have been tested to modify the hydrophilicity of these surfaces, since this is central to their biocompatibility and tribological performance in aqueous environments. Despite the large number of experimental investigations, an atomistic understanding of the effects of different dopants on carbon film hydrophilicity is still lacking. In this study, we employ ab initio calculations to elucidate the effects of B, N, and O dopants in several mechanisms that could modify interactions with water molecules and thus hydrophilicity. These include the adsorption of intact water molecules on the surfaces, minimum energy pathways for water dissociation, and subsequent interactions of hydrogenated and hydroxylated surfaces with water molecules. We find that all of the dopants considered enhance hydrophilicity, but they do so through different means. Most notably, B dopants can spontaneously chemisorb intact water molecules and increase its interactions in H-bond networks.

Deposition and characterization of tungsten oxide (WO3) nanoparticles incorporated diamond-like carbon coatings using pulsed-DC PECVD

In this study a novel approach using pulsed-DC plasma enhanced chemical vapour deposition (DC-PECVD) to incorporate tungsten oxide nanoparticles into diamond-like carbon coatings (DLC) thin film deposited on tappet valve (metallic substrate) was successfully achieved. The DLC-W film obtained by incorporating WO3 nanoparticles into DLC was characterized using scanning electron microscope/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), Raman spectroscopy, scratch test, Rockwell C indention test and nano-hardness measurement. The thickness, hardness and elastic modulus were measured as 789.11 ± 16 nm, 18.64 ± 0.11 GPa and 152.03 ± 2.1 GPa respectively. The ID/IG was 0.95, D and G peaks positioned at 1341.66 and 1562.17 cm−1 respectively and W2C was observed from the XRD. The coating had a low apparent COF of 0.075 and excellent adhesion properties.

Influence of the TixSi and TixSi/a-Si:H interlayers on adherence of diamond-like carbon coatings

The effect of two different interlayers on the adherence of DLC coatings to AISI 316 L stainless steel was studied. Titanium‑silicon (TixSi) interlayers and titanium‑silicon plus amorphous hydrogenated silicon (TixSi/a-Si:H) interlayers were deposited. TixSi intermediate layers were grown with three different thicknesses via the RF sputtering technique, while a-Si:H interlayers and DLC coatings were deposited using a DC-PECVD system with an active screen as an additional cathode. The microstructural characterization of the titanium‑silicon interlayer was carried out through the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and chemical analysis was done by means of energy-dispersive X-ray spectroscopy (EDS), while DLC coatings were studied with Raman spectroscopy. The degree of adhesion of the DLC coatings to AISI 316 L stainless steel substrates was analyzed using critical load measurements and a VDI 3198 indentation test. XRD results showed that new crystalline phases were not present in the TixSi interlayer. XPS spectra showed a bond between the SiFe and the Ti-Fe-O. The adherence results showed that the DLC coatings deposited using TixSi with 200 nm thickness exhibited a critical load value of 5 N, while the coatings with other thicknesses were completely delaminated when the same load was applied. These results suggested that the low adhesion of the DLC coating was due to the oxides formed at the TixSi-DLC interface. For the AISI 316 L/TixSi/a-Si:H/DLC coating, a critical load of 26 N was determined. The formation of titanium silicide, iron silicide, and silicon carbide in the interfaces allowed an increase in the adhesion strength between the interlayers. The Raman results showed that the DLC coatings exhibited good microstructural properties and hydrogen contents around 28 at.%. The DLC coatings also exhibited a hardness of 25 GPa.

Tribological behavior of PS400-related tribopairs for space exploration

PS400 is a multi-component alloy developed by NASA and intended for high temperature bearing applications. This study reports on four mating surfaces, namely bulk 4130 steel, diamond-like carbon (DLC), polycrystalline diamond, and molybdenum boride cobalt chrome coatings sliding against PS400 coating, and the best performing tribopair at 25 and 500 °C was identified. The temperature range and sliding speeds simulate extreme conditions for low-speed space-related applications, such as bearings on landing probes for future missions to Venus. PS400 vs. DLC showed low friction and excellent wear resistance up to 500 °C. DLC provided good lubrication at 25 °C, whereas at 500 °C oxide glazes transferred on DLC, maintaining low friction. The worn surfaces and the transfer films were analyzed using different analytical techniques.

Influence of Dimple Geometry on Coating Performance Under Uni-Directional Sliding

The 316L stainless steel as very low carbon content than 316 steel alloys and 316L is material generally used for medical implant purpose and other industrial applications because of its excellent corrosion properties. The only disadvantage with 316L is it has poor wear resistance. By surface texturing the tribological properties can be improved. DLC (Diamond Like Carbon) Coating were made over the surface texturing. DLC Coating is a nano-composite coating which has unique properties of natural diamond low friction, high hardness, and also high corrosion resistance. Various dimple structures were made on the pin to study about its performance and the ideal dimple structure is selected by using pin on disc experiment. D2 Steel disc is taken as the counter-part for this experiment.