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Diamond-like carbon (DLC) films on titanium alloy Ti6Al4V substrates were tested with nanoindentation and surface roughness to look at the hardness and roughness of the coating and substrate systems as well as their mechanical properties. The powdered titanium alloy Ti6Al4V used in the substrate specimen was produced using laser powder bed fusion, an additive manufacturing process. In this study, we investigated the influence of substrates on the nanoindentation and surface roughness of the DLC film layer with an estimated 2. 2 1 μ m thickness on Ti6Al4V substrates. The findings of the nanoindentation show that the reaction to the impact was more flexible than expected. Maximum load, residual nanoindentation depth, hardness, and modulus may influence mechanical properties. The DLC-film Ti6Al4V substrate materials' top surface roughness is measured. As a result of the increased load-carrying ability of DLC/Ti6Al4V, Ti6Al4V is a superior choice for substrate materials for DLC films, A DLC coating, measuring 2. 2 1 μ m in thickness, was applied to a Ti6Al4V substrate utilizing a 5-min chromium deposition process. The biocompatibility of the substrates plays a crucial role in determining the DLC films capacity to prolong the lifespan of bone implants. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the advantages of diamond-like carbon (DLC) films in reducing friction and lubrication to address issues such as the low surface hardness, high friction coefficients, and poor wear resistance of titanium alloys. Cr-doped DLC films were deposited by high-power impulse magnetron sputtering (HiPIMS) in an atmosphere of a gas mixture of Ar and C2H2. The energy of the deposited particles was controlled by adjusting the target powers, and four sets of film samples with different powers (4 kW, 8 kW, 12 kW, and 16 kW) were fabricated. The results showed that with an increase in target power, the Cr content increased from 3.73 at. % to 22.65 at. %; meanwhile, the microstructure of the film evolved from an amorphous feature to a nanocomposite structure, with carbide embedded in an amorphous carbon matrix. The sp2-C bond content was also increased in films, suggesting an intensification of the film's graphitization. The hardness of films exhibited a trend of initially increasing and then decreasing, reaching the maximum value at 12 kW. The friction coefficient and wear rate of films showed a reverse trend compared to hardness variation, namely initially decreasing and then increasing. The friction coefficient reached a minimum value of 0.14, and the wear rate was 2.50 × 10−7 (mm3)/(N·m), at 8 kW. The abrasive wear was the primary wear mechanism for films deposited at a higher target power. Therefore, by adjusting the target power parameter, it is possible to control the content of the metal and sp2/sp3 bonds in metal-doped DLC films, thereby regulating the mechanical and tribological properties of the films and providing an effective approach for addressing surface issues in titanium alloys. [ABSTRACT FROM AUTHOR]

In this research, nitrogen-doped diamond-like carbon (N-DLC) coatings were deposited on Nitrile Butadiene Rubber (NBR) substrates using direct current magnetron sputtering (DC-MS) under varying bias voltages. This study aimed to explore environmentally friendly, low-wear, and non-lubricating seal coatings to enhance the durability of rubber sealing products, which predominantly operate under dynamic sliding conditions. By reducing the coefficient of friction (CoF), the friction and wear on rubber products can be significantly minimized, extending their lifespan. This investigation thoroughly examined the microstructure, mechanical properties, and tribological behavior of the N-DLC films. Among the coatings, the one produced at a bias voltage of −50 V demonstrated superior hardness, elastic modulus, and the lowest CoF in comparison to those prepared with 0, −100, and −200 bias voltages. This optimal combination of properties resulted in an exceptionally low wear rate of 10−9 for the film deposited at −50 V, indicating its outstanding wear resistance. [ABSTRACT FROM AUTHOR]

This study details the creation of composite films consisting of amorphous hydrogenated diamond-like carbon (DLC) and copper on stainless steel, exploring their impact on heat transfer properties. Analysis of growth morphologies indicates the development of diamond crystals in a nanocrystalline ballas-like form on stainless steel substrates, suggesting radial growth of the crystals. Raman spectroscopy of the films reveals the presence of the T2g vibration mode of diamond crystals alongside D and G bands. The downward shift of the T2g peak to 1157 cm−1 suggests the formation of nanocrystalline diamond. Additionally, Cu–O vibration peaks are detected, attributed to atmospheric copper oxidation at the surface. Raman mapping, based on intensities corresponding to Cu–O at 450 cm−1 and the E2g phonon mode of sp2 bonded carbon at 1580 cm−1, indicates a uniform distribution of copper and DLC films. The application of a diamond-like carbon/Cu composite film significantly enhances the heat flux on the surface of stainless steel. While the uncoated surface exhibits a heat flux of 100 W/m2, the presence of DLC/Cu composite coating elevates it to 450 W/m2. [ABSTRACT FROM AUTHOR]

The plunger is the core component of the sucker rod pump. Its rapid wear and premature failure severely limit the efficiency and productivity of oil and gas production. Diamond-like carbon (DLC) films, due to their high hardness, high wear resistance and low friction coefficient, have great research prospects for the development of long-life and high-reliability sucker-rod pump plungers in oil production environments. Therefore, in this paper, to simulate the friction behaviour and influence mechanism of the DLC film in an oil production environment, three molecular dynamics friction models of Fe–Fe, DLC–Fe and DLD–DLC were established. It is found that with increasing load, the friction coefficients of DLC–Fe and DLD–DLC are smaller than that of Fe–Fe in the light oil reservoir environment. In particular, when the mating pair is DLC–DLC, a superlubricity state of 0.0007 is even achieved. This will greatly increase the service life of the plunger of the sucker rod pump in the oil production environment. Further investigation revealed that the low friction of the DLC film in an oil production environment is mainly due to the weak interaction between light oil molecules and the DLC layer, so that it does not cause adhesive wear with the friction surface while lubricating the surface. [ABSTRACT FROM AUTHOR]

Micro-scratch responses of diamond-like carbon (DLC) films deposited with different dopants (i.e., Si, Cr, and H) were investigated by Rockwell C diamond indenter under progressive normal load linearly increasing from 5 mN to 15 N. Three critical loads can be identified from residual scratch morphology according to different periodic and symmetrical damage patterns. The results under small loads show: The addition of H can enhance normal contact and residual hardness of DLC films. Fracture toughness of both film and film/substrate system can be quantified by scratch-based linear elastic fracture mechanics. H-DLC film exhibits the smallest fracture toughness, and Si-DLC and Cr-DLC films have larger fracture toughness and critical loads than pure DLC film. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films with excellent anti-friction and wear resistance, can effectively reduce the energy loss of tribosystems and the wear failure of parts, but the high residual stress limits their application and service life. Researchers found that doping heterogeneous elements in the carbon matrix can alleviate the defects in the microstructure and properties of DLC films (reduce the residual stress; enhance adhesion strength; improve tribological, corrosion resistance, hydrophobic, biocompatibility, and optical properties), and doping elements with different properties will have different effects on the structure and properties of DLC films. In addition, the comprehensive properties of DLC films can be coordinated by controlling the doping elements and their contents. In this paper, the effects of single element and co-doping of carbide-forming elements (Nb, W, Mo, Cr, Ti, Si) and non-carbide-forming elements (Cu, Al, Ag, Ni) on the properties of microstructure, mechanical, tribological, optical, hydrophobic, corrosion resistance, etc. of DLC films are reviewed. The mechanisms of the effects of doping elements on the different properties of DLC films are summarized and analyzed. [ABSTRACT FROM AUTHOR]

In this research, nitrogen-doped diamond-like carbon (N-DLC) coatings were deposited on Nitrile Butadiene Rubber (NBR) substrates using direct current magnetron sputtering (DC-MS) under varying bias voltages. This study aimed to explore environmentally friendly, low-wear, and non-lubricating seal coatings to enhance the durability of rubber sealing products, which predominantly operate under dynamic sliding conditions. By reducing the coefficient of friction (CoF), the friction and wear on rubber products can be significantly minimized, extending their lifespan. This investigation thoroughly examined the microstructure, mechanical properties, and tribological behavior of the N-DLC films. Among the coatings, the one produced at a bias voltage of −50 V demonstrated superior hardness, elastic modulus, and the lowest CoF in comparison to those prepared with 0, −100, and −200 bias voltages. This optimal combination of properties resulted in an exceptionally low wear rate of 10−9 for the film deposited at −50 V, indicating its outstanding wear resistance.

The service conditions of rubber seals are primarily in the dynamic sliding state, with a high coefficient of friction, which can seriously compromise the equipment’s safety and the services’ lifespan. Diamond-like carbon (DLC) films have been the ideal candidate for tribological modification of rubber surfaces due to their excellent tribological properties over the last two decades. This field can be widely discussed as a hard film on soft substrates, where the challenge is the mismatch of mechanical properties, leading to the exfoliation of DLC films in friction. Early work developed the DLC films with a segment structure to solve this critical issue, illustrating the possibility of wear-resistant rubber. In recent years, researchers have paid attention to further increasing the coated rubber’s lifetime in friction, focusing on adhesion. These research achievements were reviewed on the aspects of structurization, adhesion, and doping in this article. It proposed an alternative direction of understanding the surface wear mechanism for designing wear-resistant DLC films on rubber.

DLC (diamond-like carbon) films were prepared on Ti/PMMA(polymethyl methacrylate) under the different bias; the principal purpose of this study is to explore structural differences of films on Ti/PMMA with and without conductive material, and to further clarify the role of the conductive Ti interlayer in influencing the deposition mechanism. The results indicate that the films deposited on Ti/PMMA with conductive material exhibit uniform DLC structure and mechanical hardness when the bias voltage is ≥550 V. Furthermore, the deposited DLC does not change the wettability of PMMA, while the addition of the Ti interlayer virtually increases the risk of peeling off of the film. The results of the tribological study demonstrate the films on Ti/PMMA with conductive material have better tribological properties than those without conductive adhesive. This research work can provide basic theoretical guidance for depositing uniform DLC films on PMMA and even on all non-conductive substrates. [ABSTRACT FROM AUTHOR]

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DLC films were deposited on Si substrates using direct ion beam deposition method, followed by investigating the influence of O2 and N2 doping on their electrical and structural properties. The films were doped with oxygen and nitrogen under flow rates of 5 and 40 sccm (standard cubic centimeters per minute). The structure of the films was studied by Raman spectroscopy. Result showed that by increasing oxygen incorporation, sp2 content decreases, sp3 content increases, and the C-C bonding loses its order. As the size of the sp2-rich cluster increased with N2 content, the disorder in the DLC samples decreased, leading to a decrease in the FWHM of the G peak. The water contact angle measurement showed that an increase in oxygen flow ratio results in a decrease in contact angle from 82.9° ± 2.1° to 50° ± 3°. With increasing nitrogen flow rate from 5 to 40, the contact angle of DLC thin films increased from 78° to 110°.

Doped DLC film is expected to be a vital surface protection material in aerospace and other important fields. However, the long experiment cycle for screening efficient dopants, premature failure caused by high residual stress, and insufficient understanding of the microscopic mechanism, seriously limit its further improvement. In this work, the performance prediction and mechanism study of doped DLC films were proposed by combining molecular dynamics (MD) and first-principles calculations, and the commonly used Si and MoS 2 were selected as the typical elemental and compound dopants for investigations, respectively. MD was used to evaluate the influence of both the type of dopant and its amount on the structure and properties, including the content of sp2-C and sp3-C, hardness, elastic modulus, and friction coefficient of DLC films. First-principles calculations were performed to study the modification mechanism of Si and MoS 2 dopants from a viewpoint beyond the experimental scale. This study was verified by experimental investigation and proven to make a fast prediction and screening for the doping craft of DLC films. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the tribological properties of two diamond-like carbon (DLC) films were investigated at different temperatures using water-engine oil emulsions as lubricants, considering emerging fuel systems such as hydrogen and ammonia. The results revealed that the friction coefficient of a-C film raised with the increasing water content at 80 °C. The friction coefficient of a-C:H film initially raised and then decreased with varying water fractions at different temperatures. Elevated temperature exacerbated the wear of both DLC films at high water contents. The most significant wear was observed for a-C film at 80 °C and a-C:H film at 50 °C. The a-C:H film exhibited more sensitive wear characteristics to water content than the a-C film. Surface analysis indicated that water-engine oil emulsions prevented the formation of phosphate tribo-film on steel friction pair for two DLC films but promoted the tribo-oxidation of steel pair sliding contact with a-C film, especially at higher temperatures. Distinct reactivities of two DLC films towards water molecules could affect the adsorption of lubricants on DLC surfaces, leading to their different friction and wear behavior. It suggests that the water-caused emulsification of lubricating oil will be a pivotal consideration in tribological applications of DLC films in future internal combustion engines. [Display omitted] [ABSTRACT FROM AUTHOR]

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.

Diamond-like carbon (DLC) films with excellent anti-friction and wear resistance, can effectively reduce the energy loss of tribosystems and the wear failure of parts, but the high residual stress limits their application and service life. Researchers found that doping heterogeneous elements in the carbon matrix can alleviate the defects in the microstructure and properties of DLC films (reduce the residual stress; enhance adhesion strength; improve tribological, corrosion resistance, hydrophobic, biocompatibility, and optical properties), and doping elements with different properties will have different effects on the structure and properties of DLC films. In addition, the comprehensive properties of DLC films can be coordinated by controlling the doping elements and their contents. In this paper, the effects of single element and co-doping of carbide-forming elements (Nb, W, Mo, Cr, Ti, Si) and non-carbide-forming elements (Cu, Al, Ag, Ni) on the properties of microstructure, mechanical, tribological, optical, hydrophobic, corrosion resistance, etc. of DLC films are reviewed. The mechanisms of the effects of doping elements on the different properties of DLC films are summarized and analyzed.

Diamond-like carbon (DLC) films directly deposited on rubber substrate is undoubtedly one optimal option to improve the tribological properties due to its ultralow friction, high-hardness as well as good chemical compatibility with rubber. Investigating the relationship between film structure and tribological performance is vital for protecting rubber. In this study it was demonstrated that the etching effect induced by hydrogen incorporation played positive roles in reducing surface roughness of DLC films. In addition, the water contact angle (CA) of DLC-coated nitrile butadiene rubber (NBR) was sensitive to the surface energy and sp2 carbon clustering of DLC films. Most importantly, the optimum tribological performance was obtained at the 29 at% H-containing DLC film coated on NBR, which mainly depended on the following key factors: (1) the DLC film with appropriate roughness matched the counterpart surface; (2) the contact area and surface energy controlled interface adhesive force; (3) the microstructure of DLC films impacted load-bearing capacity; and (4) the generation of graphitic phase acted as a solid lubricant. This understanding may draw inspiration for the fabrication of DLC films on rubber to achieve low friction coefficient. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) based films are usually applied to devices as protective coating in devices demanding excellent mechanical properties in order to improve tribological performances. In this work, DLC/Ti double-layer thin films were deposited on a moving part of Heads Gimbal Assembly (HGA) tester and were put in the operation for 1000 h. Comparison of structural properties of the newly deposited and after full operation samples was investigated. Surface morphology was examined by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used for examining chemical composition of films. Moreover, the structural properties were studied by near edge X-ray absorption fine structure (NEXAFS) spectroscopy and Raman spectroscopy. The results show a good tribological performance of the film as there was no significant difference between the new and used sample. [ABSTRACT FROM AUTHOR]

Diamond-like carbon films were deposited on the polymer PEEK surface using a magnetron sputtering system. Experiments were conducted under varying rotational friction speed conditions. Special attention was devoted to assessing the surface condition of spherical spots post-friction experiments. Optical microscopy, friction tester, Raman spectroscopy, XPS analysis, and atomic force microscopy were employed to examine film surface morphology, atomic bonding structure, and surface roughness. The results indicate that thin film wear trace exhibits a graphitization trend that increases and then decreases, peaking around 350 rpm (0.11 m/s). Conversely, for spherical spots, the graphitization pattern is the opposite, suggesting a higher degree of disorder in the transferred film on these spots. XPS analysis reveals multiple chemical bonding structures between carbon and oxygen elements on the spherical spots. Notably, under the optical microscope, spherical spots exhibit clear directional alignment, which is absent on the film surface. This study introduces an innovative approach for producing diamond-like carbon films with lubricating and anti-wear properties. It also provides guidance for designing high-performance polymer tribo-systems in industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the tribological behavior and interface material evolution of H-free DLC film were investigated under current-carrying conditions in dry contact, using 9Cr18 steel balls as counterparts. Friction surfaces were examined using scanning electric microscopy, energy dispersive spectroscopy, and Raman spectra. Results showed that high current leads to obvious friction instability. The current direction significantly affects the friction behavior of the DLC film/9Cr18 steel contact. When the forward current increased to 1.0 A, DLC film severely wore, and local DLC film detachment occurred within sliding tracks. Graphite-like carbon was transferred to 9Cr18 steel ball surfaces in some cases but it did not show a good correlation with the friction behavior changes of DLC film. Based on elemental analysis, the formation of metal oxides on steel surface may influence the friction and wear behavior of DLC/9Cr18 steel contact under current-carry conditions. Additionally, the current clearly induces the graphitization transformation of DLC carbon matrix depending on the specific current conditions, which accelerates the wear of DLC film. [Display omitted] [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films embedded with crystalline graphite and multilayer graphene have been fabricated on silicon substrates by a simple electrochemical route from methanol and C60-1, 2-ethylenediamine (C2H8N2) derivatives as an incorporating reagent at atmospheric pressure. The structure and sheet resistivity of the as-obtained films were characterized by x-ray photoelectron spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and four-point probe measurements, respectively. The structure of the as-prepared films with crystalline graphite and multilayer graphene consisted of sp2 C, sp3 C, C–N, C–H, and N–H bonds. After introducing crystalline graphite and multilayer graphene, the conductivity of the DLC films was evidently improved and the sheet resistivity drastically decreased from 108 Ω cm to about 80 Ω cm. [ABSTRACT FROM AUTHOR]

To investigate the effects of Cr doping on the microstructure and tribological properties of multi-layered diamond-like carbon (DLC) films, Cr-DLC films with Cr contents ranging from 0 to 22 at.% were deposited on 0Cr19Ni10 stainless steel and Si wafer surfaces by unbalanced magnetron sputtering. The thickness of the transition layer is 180 nm and the Cr-DLC film ranging from 1.3 to 1.5 µm. The microstructure, mechanical and tribological properties of the films were systematically investigated at room temperature in atmospheric environment. Results show that increasing the Cr target current can effectively improve the incident particle density and reduce surface roughness. As a strong carbon metal, Cr has significant influence on the structure and properties of the film for bonding with carbon atoms during deposition. High-energy Cr particles are favorable for films to increase the sp3 hybrid bond ratio and reduce internal stress. The high-hardness sp3 hybrid phase, Cr carbide, oxide dispersion can effectively improve the mechanical properties of the film, but overdoping is detrimental for mechanical properties of the film. The internal stress shows a continuous trend of decreasing with the increasing Cr content and it reduced up to 80% compared with pure DLC films. The films prepared with Cr sputtering current of 0.4 A demonstrate the best tribological properties, and the friction coefficient and wear rate are 0.15 and 2.9 × 10−7 mm3/Nm, respectively. [ABSTRACT FROM AUTHOR]

Tribological behaviors of three typical kinds of diamond‐like carbon (DLC) films (a‐C, a‐C:Cr, and a‐C:H) in sulfuric acid and sodium hydroxide solutions were investigated. The a‐C film showed the lowest stable coefficients of friction (COF) in both sulfuric acid and sodium hydroxide solutions but the worst wear resistance in sulfuric acid solution. The a‐C:H film showed the highest COF in sulfuric acid solution and the best wear resistance in both sulfuric acid and sodium hydroxide solutions. The a‐C:Cr film exhibited superior comprehensive tribological performance in sulfuric acid solution, while in sodium hydroxide solution, high COF and very poor wear resistance was observed. What is more, friction and wear mechanism was revealed by investigating the friction‐induced material evolutions on the sliding surface. [ABSTRACT FROM AUTHOR]

Utilizing a diamond-like carbon (DLC) coating on rubber surfaces is an innovative approach to improve the wear resistance and tribological characteristics of rubber. In this paper, a series of N-doped diamond-like thin films (N-DLC) were deposited on the surface of nitrile butadiene rubber (NBR) substrate by varying the flow rate of nitrogen using direct current magnetron sputtering (DC-MS) technology, and the effects of nitrogen flow rate on the surface morphology, structure, surface energy and tribological properties of N-DLC films were systematically investigated. The results show that the friction coefficients of the N-DLC films are all smaller than those of the undoped DLC films, and most importantly, the samples maintain a stable, ultra-low coefficient of friction of about 0.057 and a low wear rate of the order of 10−9 in the tribological tests at a nitrogen flow rate of 3 sccm, exhibiting excellent tribological performance. This is attributed to several key factors: higher hardness, better film-base bonding, lower surface roughness, and lower friction interface adhesion. This recognition provides insight into the preparation of N-DLC films on rubber to achieve low frictional wear. • A method to improve the tribological properties of NBR by using N-DLC films. • Modified NBR has an ultra-low coefficient of friction and low wear rate. • N 2 flow rates significantly affect properties of N-DLC films on NBR surfaces. • The tribological performance is optimal at a nitrogen flow rate of 3 sccm. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films were electrochemically deposited onto indium tin oxide (ITO) substrates using acetic acid and deionized water as electrolyte at low deposition voltages (2.4 V and 60 V). The transmittance of the films was investigated by UV spectrometry. Transmittance measurements versus wavelength revealed that the films transmit 86 % to 89 % light in visible region and band gap of the films varies between 3.87 eV and 3.89 eV. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used for structural characterization to evaluate surface morphology of the DLC films. The grain size and the surface roughness increased for the films prepared at higher deposition potential, while their measured average height decreased. The mechanical properties (hardness H and elastic modulus Er) were determined from load-displacement curves which were obtained by using nanoindentation method. Hardness and elastic modulus of the films increased as the deposition voltage of the films increased from 2.4 V to 60 V. [ABSTRACT FROM AUTHOR]

Abstract Vacuum arc was used to prepare Cr/CrN/DLC films on different textured surfaces fabricated by femto-laser, and the influences of textures with different patterns, sizes, and orientations on structures, adhesion and mechanical properties of Cr/CrN/DLC films were investigated. The physical and chemical characteristics of DLC films were studied by scanning electron microscopy (SEM), Raman. Morphology instrument was used to test the chemical structure and surface topography. Adhesive strength and anti-wear properties were measured by scratch tester and SRV micro-tester. The results showed that micro-structures improve the contents of sp3 in DLC film, and also affect the adhesive strength and anti-wear properties of DLC films by increasing interval from 150 to 350 μm, which was processed by femto-laser under 0.96 power density, 400 mm/min processing speed. The experiment certificated that DLC film on stripe structure with 250–350 μm interval showed best properties, the wear rate of DLC film with 250 μm interval was lower than 1.35 × 10−6 mm3/Nm, and the adhesion strength of film was up to 52 N on stripe micro-structure separated around 350 μm. The results showed that femto-second ultrafast laser has little influence on substrate, the textured surface improved the sp3 contents in DLC films with suitable size. Compared to the DLC film without micro-structure, the best anti-wear properties of DLC film with textured interface with 250 μm interval were enhanced up to 50 times. Highlights • Femto-second laser has little influence on textured substrate under 0.96J/cm2, 400 mm/s. • Micro-structure with 250-350 μm intervals improved the contents of sp3 in DLC film. • Wear rate of DLC films on 250μm stripe and lattice structure was 50 times lower than DLC film without structure. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hollow cathode discharges were affected by the applied magnetic field intensity. • Cutoff condition for tube-20 occurred at B-fields lower than theoretically predicted. • The degree of disordering of DLC films was increased by using the magnetic field. • PIII&D with magnetic field resulted in DLC films with defect-free morphology. Abstract Hollow cathode discharges were evaluated under the effects of the E × B crossed fields for deposition of DLC (Diamond-like Carbon) films. The stabilities of various plasma discharges, as well as, the produced plasma confinement were enhanced significantly with the magnetic field application. Experimental tests corroborate the positive action of E × B mechanism for the improvement of PIII&D (Plasma Immersion Ion Implantation and Deposition) in metal tubes. As regards to the structure of the obtained carbon films, the magnetic field application improves their diamond-like character. Magnetically confined plasmas resulted in DLC films with defect-free morphology and lower roughness. Using this type of PIII&D setup is highly recommended for inner surface coating of tubes when highly disordered DLC films are required. [ABSTRACT FROM AUTHOR]

This paper focuses on the Cr interlayer effect on the structure and properties of Cr/DLC films. To improve structural, mechanical and chemical properties of a-C films, we developed two layer chromium-carbon films produced by cathode magnetic filtered arc deposition. Microstructure and properties of these films are explained depending on the Cr-interlayer size. The structure is analyzed by Raman spectroscopy. Moreover, we also estimated residual stress, the friction coefficient, hardness, the elastic modulus and corrosion parameters by X-ray double crystal surface profilometry, tribotesting, nanoindenter-testing, as well as contact angle measurements and potentiodynamic polarization analysis. As a result of the comparative analysis, we revealed a substantial improvement in the characteristics of the produced two layer films. The results provide theoretical basis for the application of these films.

Abstract Nitrile-butadiene rubber (NBR) exhibits the high friction and wear as a dynamic seal sliding against the engineering materials. To improve its friction and wear resistance, diamond-like carbon (DLC) films are devised to deposit on NBR rubber via plasma-enhanced chemical vapor deposition (PECVD). Prior to the deposition, Ar plasma pretreatment of NBR substrate is carried out, and the influence of Ar plasma pretreatment time on the adhesion and tribological behavior of DLC coated NBR is studied systematically. The typical micrometer- scale patches divided by random cracks are always observed on the DLC film coated NBR rubber, and the size of the patches increases with increasing pretreatment time. Moreover, the hardness of the films decreases monotonously as the increase of the pretreatment time, which means that Ar plasma pretreatment has an effect on the properties of the films. It is worth to mention that the adhesion strength between DLC films and rubber first increases and then decreases along with the change of Ar plasma pretreatment time. The tribotests results show that the DLC film with 30 min pretreatment exhibits the lowest friction coefficient of 0.2 (compared to ~0.8 of uncoated NBR) during 12,000 laps. The wear life of the superior DLC/NBR is studied further, and it is functional after 120,000 laps tribotests under the normal load of 10 N. Therefore, the DLC film can be considered as a promising candidate coating for the enhancement of wear resistance of rubbers. Graphical abstract Unlabelled Image Highlights • The sp2 content of DLC films increases with the increase of Ar plasma pretreatment time. • A high adhesion could be obtained by a suitable Ar plasma pretreatment time. • The proportion of free radicals is obtained by oxygen element mapping images. • The optimum DLC/NBR is functional after 120000 laps tribotests under the normal load of 10 N. [ABSTRACT FROM AUTHOR]

This paper presents the results of investigations of carbon films deposited by a modified version of the magnetron sputtering method – HiPGIMS (High Power Gas Injection Magnetron Sputtering). In this experiment, the magnetron system with inversely polarized electrodes (sputtered cathode at ground potential and positively biased, spatially separated anode) was used. This arrangement allowed us to conduct the experiment using voltages ranging from 1 to 2 kV and a power supply system equipped with 25/50 μF capacitor battery. Carbon films were investigated by VIS/UV Raman spectroscopy. Sp 3 /sp 2 bonding ratio was evaluated basing the elementary components of registered spectra. Our investigation showed that sp 3 bond content increases with discharge power but up to specific value only. In extreme conditions of generating plasma impulses, we detected a reversed relation of the sp 3 /sp 2 ratio. In our opinion, a energy of plasma pulse favors nucleation of a sp 3 phase because of a relatively higher ionization state but in extreme cases the influence of energy is reversed. [ABSTRACT FROM AUTHOR]

Necessary conditions for usage of DLC coated mechanical seals were investigated by using ring on ring type sliding tests under various contact pressures and sliding speeds in dry and wet nitrogen. The wear mode of DLC coated SiC mechanical seal can be classified into two types by surface morphology of wear surface called ModeI with smooth surface that is useful as a seal and ModeII with relatively rough surface. The transition condition from ModeI to II is given by a critical μ2PV value, and show 0.025 under dry nitrogen and 0.070 under wet nitrogen. With the increase in PV value, arithmetic average roughness Ra decreases from 0.06 μm to 0.04 μm, and it leads to reduction of friction coefficient from 1.4 to 0.4. On the other hand, structural change of DLC films was not obtained within the condition of Mode I, and the friction was high. ModeI possibly has the desirable condition to DLC films for mechanical seal use. As a conclusion, the operation within critical μ2PV value range which depends on various conditions, and in addition, reduction of the friction coefficient in this range, achieve the increase of operating condition.

Ultralow friction is achieved by ZrO2 as the friction mate material for DLC (Diamond like carbon) films under various environments. Coefficient of friction (CoF) of ZrO2/DLC films is as ultra low as 0.02 in ambient air at the temperature of 200 °C, and 0.03, 0.04 and 0.05 in hydrogen, nitrogen and vacuum environments at the temperature of 100 °C, respectively. It is concluded that the transferred films are formed on the worn surface of ZrO2 ball and amorphous carbon films. Ultralow friction of the friction pair is related with hydrogen, which is derived from DLC films, hydrogen environment or the liberation hydrogen due to hydrothermal oxidation. The ultralow friction mechanism is attributed to the formation of hydrogenated amorphous carbon films on ZrO2 ball and the shielding action of hydrogen from DLC films and the transferred films simultaneously. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films with F and Si co-doping (DLC:F:Si films) were deposited on medical 316 L stainless steel substrates with radio frequency reactive magnetron sputtering by using trifluromethane (CHF 3 ) and argon as source gases and SiC crystal target. The relations between the RF input powers and adhesion behavior of DLC:F:Si films were investigated. Surface morphology and roughness, hardness, sp 2 /sp 3 hybridization ratio, and bonding configuration were characterized subsequently to demonstrate the adhesion evolution by Atomic force microscope (AFM), nanoindenter, Raman spectrometer, Fourier-transform infrared (FTIR) spectrometer and Friction and wear tester. The relative intensity of the CF symmetric stretch vibration (1160 cm − 1 ) to CF 2 asymmetric stretch vibration (1220 cm − 1 ) and HFC C < stretch vibration (1620 cm − 1 ) to F 2 C C < stretch vibration (1710 cm − 1 ) as a function of RF input powers were especially demonstrated. The results show that choosing a appropriate RF input power can effectively modulate the structure and adhesion characteristics of DLC:F:Si films. The DLC:F:Si films prepared at about 200 W RF input power have stable bond configuration and exhibit good adherence, hardness and wear resistance. [ABSTRACT FROM AUTHOR]

Deposition of hard and adherent diamond-like carbon (DLC) coatings employing an asymmetrical bipolar pulsed-DC PECVD system and an active screen that functioned as an additional cathode is presented. This novel system represents a step forward for thin coating growth by using much lower pressure (about 0.1 Pa) in an almost collision-less regime, with higher plasma density than the conventional PECVD system. In order to overcome the low adherence of DLC coatings to 316 stainless steel substrates, a thin amorphous silicon interlayer was deposited as an interface. The interlayer was synthesized using silane as precursor gas and varying the applied DC bias voltage during deposition. The DLC coatings were produced using acetylene gas as the precursor. Both the amorphous silicon interlayers and the DLC films were analyzed according to their microstructural, mechanical, and tribological properties as a function of the applied substrate bias voltage. The film's atomic arrangements were estimated by means of Raman spectroscopy, while the hydrogen content was determined via elastic recoil detection analysis (ERDA). The nanoindentation experiments helped determine the films' hardness and other nanomechanical parameters. The friction coefficient was determined using a tribometer in unlubricated sliding friction experiments, while the adhesion of the films was determined through a classic Rockwell C indentation test. The results showed an improvement of the properties and the adherence of the DLC coatings deposited using a modified experimental setup and an amorphous silicon interlayer. The composition, microstructure, and mechanical and tribological properties of the films were dependent on the applied DC bias voltage and, consequently, on the intensity of ion bombardment during coating growth. These results suggest that a combination of a modified pulsed-DC PECVD system, the use of an active screen as an additional cathode, and acetylene as a precursor gas for growing DLC films may represent a new and useful alternative for mechanical and tribological applications. [ABSTRACT FROM AUTHOR]

Diamond like carbon films (DLC) with high density and low internal stress are urgent demand for inertial confinement fusion (ICF) experiments. DLC films were deposited on Si-(100) substrates by coupling DC/RF magnetron sputtering with Ar as the working gas. The microstructure, mass density and internal stress of the DLC films have been studied. The films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray Reflectivity (XRR), surface profilometer, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), scratch test and nanoindentation techniques. It is found that the DLC films deposited by coupling DC/RF magnetron sputtering have relatively high mass density (2.25–2.36 g/cm 3 ) and low internal stress (lower than 0.3 GPa) compared to those prepared by conventional deposition process. The results indicate that properties of the as-deposited DLC films are strongly dependent on the ion energy which is determined by the DC voltage. It suggests that the DLC films deposited by coupling DC/RF magnetron sputtering at optimum DC voltage could be potential candidate for ICF experiments and protective coating applications. [ABSTRACT FROM AUTHOR]

This paper focuses on the Cr interlayer effect on the structure and properties of Cr/DLC films. To improve structural, mechanical and chemical properties of a-C films, we developed two layer chromium-carbon films produced by cathode magnetic filtered arc deposition. Microstructure and properties of these films are explained depending on the Cr-interlayer size. The structure is analyzed by Raman spectroscopy. Moreover, we also estimated residual stress, the friction coefficient, hardness, the elastic modulus and corrosion parameters by X-ray double crystal surface profilometry, tribotesting, nanoindenter-testing, as well as contact angle measurements and potentiodynamic polarization analysis. As a result of the comparative analysis, we revealed a substantial improvement in the characteristics of the produced two layer films. The results provide theoretical basis for the application of these films. [ABSTRACT FROM AUTHOR]

Ultralow friction is achieved by ZrO2 as the friction mate material for DLC (Diamond like carbon) films under various environments. Coefficient of friction (CoF) of ZrO2/DLC films is as ultra low as 0.02 in ambient air at the temperature of 200 °C, and 0.03, 0.04 and 0.05 in hydrogen, nitrogen and vacuum environments at the temperature of 100 °C, respectively. It is concluded that the transferred films are formed on the worn surface of ZrO2 ball and amorphous carbon films. Ultralow friction of the friction pair is related with hydrogen, which is derived from DLC films, hydrogen environment or the liberation hydrogen due to hydrothermal oxidation. The ultralow friction mechanism is attributed to the formation of hydrogenated amorphous carbon films on ZrO2 ball and the shielding action of hydrogen from DLC films and the transferred films simultaneously.

In order to obtain super-hard films with excellent mechanical and tribological properties, diamond-like carbon (DLC) films were prepared on ultra-fine grained cemented carbide substrates by linear magnetic filtered arc ion plating (AIP) under different negative pulsed bias voltages. The result indicated that the pulsed bias voltage had a strong effect on the structure and properties of DLC films. The as-deposited films showed very smooth surfaces because of the magnetic filtration system. Upon increasing the bias voltage from 0 to −1000 V, the fraction of sp3 bonds first increased and then decreased, while the ratio I D / I G exhibited the opposite tendency. The maximum sp3 bond fraction of 74.4 % was determined at −200 V, resulting in the highest hardness, elastic modulus, and elastic recovery of the films. Furthermore, the films exhibited excellent tribological properties with the lowest friction coefficient of 0.073 at −200 V, which was associated with the super-high hardness and low surface roughness. The improved mechanical and tribological properties of DLC films could be achieved by using the appropriate pulsed bias voltage. [Display omitted] • The super-hard DLC films were successfully developed by arc ion plating with the pulsed substrate bias. • The arc deposited DLC films exhibited the smooth and dense surface because of the synergy effect of macroparticle filtering and re-sputtering • The maximum hardness and excellent tribological properties were obtained at – 200 V. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films were deposited on three-dimensional (3D) shape substrate model by electrolysis of 2-propanol solution at low temperature (60 °C). This 3D shape model was composed of a horizontally aligned stainless steel wafer and vertically aligned stainless steel rods. Morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy, respectively. The results suggested there were only differences in film uniformity and thickness for two kinds of samples. The hydrogenated amorphous carbon films deposited on horizontally aligned substrate were smooth and homogeneous. And the film thickness of DLC films gained on the vertical substrates decreased along vertical direction. It is believed that bubble formation could enhance nucleation on the wetted capillary area. This experiment shows that deposition of DLC films by liquid phase deposition on 3D shape conductive substrates is possible. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-step growth of DLC films with nanocrystal phase on glass substrate, without diamond powder pre-treatment. • Inductively coupled low-pressure high electron-density (CH 4 + Ar) plasma used for the film deposition. • Optimum DLC film obtained at –40 V dc substrate-bias, 450 °C, 900 W rf power and 25 sccm CH 4 flow. • DLC film showed [I D /I G ] min ∼0.61 with [I Dia /I D ] max ∼1.09 in Raman and ~64% of sp3 bonds in XPS data. • DLC film exhibited wide optical band gap ∼3.71 eV and 〈1 1 1〉 nanocrystal facets in the network. Working at relatively low-temperature and low-pressure, the development and optimization of diamond-like carbon (DLC) films with significant nanodiamond components on inexpensive glass substrates, without conventional pre-treatment by diamond powders, is the main objective of the present work. Using the most familiar CH 4 -precursors diluted by Ar in a high-density plasma triggered at high rf power (900 W) in a planar inductively-coupled plasma chemical vapour deposition (ICP-CVD) system, DLC thin-films are prepared via optimization in the flow rate of the precursor gas at 30 mTorr (∼4 Pa) pressure and 450 °C substrate temperature and, further by applying negative dc-bias to the substrates. The optimized samples obtained with negative substrate-bias possess good crystalline properties. From Raman results, the most crystalline sample is obtained with characteristic minimum I D /I G ratio reduced from 0.75 to 0.61, maximum I Dia /I D enhanced from 0.94 to 1.09, and the sp3 hybridized C C bonds increased from 44% to ∼64% at a substrate-bias of –40 V. The residual stress, and the optical band gap were calculated from Raman analysis. The optimized DLC film exhibits a high optical band gap (3.71 eV) as calculated from Tauc's plot analysis of the UV–Vis data. The well-identified 〈1 1 1〉 crystallographic planes in the TEM micrograph demonstrate a significant fraction of nanocrystalline diamond component in the optimum DLC film. [ABSTRACT FROM AUTHOR]

Hydrogenated diamond-like carbon coatings (DLCs) with Cr/WC + C interlayers were deposited using a plasma-enhanced chemical vapor deposition (PECVD) method onto the surface of M35 high-speed alloys suffered by various pre-treatments including annealing and deep cryogenic cooling. Scanning electronic microscopy, transition electronic microscopy, X-ray diffractometry, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the microstructure, and hardness indentation, scratch testing, and friction testing were used to measure the mechanical performance of the DLCs. The results showed that different pretreatments led to variations in the microstructure of the M35 alloy, which influenced the coating growth process. Although all the pretreatments resulted in the same fraction of carbon-hybrid structures of the top DLC layer, the best combination of adhesion strength, hardness, friction, and wear resistance was found when the alloy was tempered at 525 °C for 1 h, followed by cryogenic treatment at −180 °C for 6 h. In contrast with the DLC deposited onto M35 alloy substrate pretreated by only 525 °C for 1 h tempering, the above pretreatment could improve adhesion force by 20 %, hardness by 15 %, and wear resistance by approximately 50 %. [Display omitted] • Tuning the microstructure of an M35 alloy by a pretreat • Depositing DLCs onto M35 by PECVD • Improving adhesion and wear resistance of DLC by a suitable pretreat • Pretreat affecting the surface morphology of DLC rather than bonding structure [ABSTRACT FROM AUTHOR]

Because coining dies are consumables, most of mints have adopted the hard surface coating on coining dies in order to increase the wear resistance of them. Even though coining dies for “proof coins” are coated by Cr-plating, they have especially short life time. Instead of Cr-plating, we tried to apply Diamond-Like Carbon (DLC) film for proof coins. In order to examine the effect of the DLC films, proof coins were actually produced with the DLC coated dies. In consequence, the die life using DLC coating is estimated to be more than twice as long as that for Cr-plating. [ABSTRACT FROM AUTHOR]