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Thick diamond‐like carbon (DLC) coatings with different silicon (Si) transition layer thickness are deposited by hollow cathode plasma immersion coating technology. The results show that the internal stress of the coating can be tuned by changing the deposition time of Si transition layer, thereby obtaining good adhesion strength. Friction and wear results show that all coatings have good tribological properties. The coating with 8 min Si transition layer (Si‐8) demonstrates the lowest friction coefficient (μ ≈ 0.03), even achieves ultralow friction (μ ≈ 0.008) for a short time. However, the wear rate of Si‐8 coating is found to be the largest (2.1 × 10−16 m3 (N m)−1. The low friction coefficient of Si‐8 coating is related to its high degree of graphitization, complete transfer film and fine wear debris. In contrast, the Si‐16 coating has the lowest wear rate of about 5.6 × 10−17 m3 (N m)−1 with a relatively high friction coefficient (μ ≈ 0.1). This is due to its high hardness and the formation of a nano‐twisted double helix carbon debris during the friction process. This nano‐twisted double helix structure can consume additional plastic deformation energy, while reducing the interface contact area and increasing the interface bearing capacity, thereby improving the wear resistance of the thick DLC coating. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) coatings, as an excellent wear-resistant and low friction material, have been successfully applied as the surface protection and lubrication of various components. Recently, its application in the pipe fittings has gradually attracted the attention of the industry. In this paper, a plasma enhanced chemical vapor deposition (PECVD) technology was used to deposit a thick Si/Si-DLC/DLC multilayer composite coating inside a high aspect ratio pipe. The experimental results showed that the structures and properties of coatings strongly depended on deposition pressures. As the deposition pressure increased, the average thickness of the coating increased from 17 μm (50 mTorr) to 21.2 μm (110 mTorr) and its uniformity deviation continued to decreased until the pressure exceeded 100 mTorr, which reached the minimum value of 35.3%. When the deposition pressure rose, the coating hardness peaked at about 18.11 GPa (70 mTorr), and then it decreased to 14.86 GPa (110 mTorr). The friction coefficient and wear rate of the coating first decreased to 0.12 and 7.37 × 10−9 mm3/Nm (70 mTorr), respectively, and then slightly increased as the deposition pressure increased. In addition, the DLC coating we deposited also achieved a high adhesion strength of about 32 N (70 mTorr). In summary, the coating prepared at 70 mTorr had the best overall performance and was promised to be applied in pipeline protection industry. Unlabelled Image • Thick Si/Si-DLC/DLC multilayer coatings were deposited inside of long pipes by PECVD method. • The thickness and uniformity of the coating increase as the deposition pressure increases. • The coating prepared at 70 mTorr has the best tribological and mechanical performance • The main wear mechanism of thick DLC coatings is plowing and flaking. [ABSTRACT FROM AUTHOR]

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp2 hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating. [ABSTRACT FROM AUTHOR]

Cr-doped amorphous carbon (a-C:Cr) film is a promising protective coating to extend the lifetime of Co–Cr–Mo implants. Here, a-C:Cr films with the same doping concentration of Cr and thickness are deposited on Co–Cr–Mo substrates using the closed-field unbalanced magnetron sputtering (UBMS) and the plasma-enhanced chemical vapor deposition (PECVD) methods. A comparative study on the microstructure, bio-tribological behavior, and cytocompatibility of two kinds of a-C:Cr films in the air and different simulated body fluids is conducted. Microstructural analysis results show that the a-C:Cr films prepared by UBMS and PECVD methods belong to graphite-like carbon (GLC) and diamond-like carbon (DLC) films, respectively. Nanohardness of the UBMS a-C:Cr film is found to be lower than that of the PECVD counterpart. However, the UBMS a-C:Cr film exhibits better lubrication, lower wear depth and lower wear volume under all the three simulated body fluids, because of the slight polishing wear and boundary lubrication mechanisms. Moreover, both kinds of a-C:Cr films significantly improve the cytocompatibility of Co–Cr–Mo substrate alloy. • Two vapor deposition methods are used to fabricate a-C:Cr films. • Microstructure, bio-tribological properties and cytocompatibility are comparatively studied. • Different deposition methods lead to different microstructures and bio-tribological properties. • The wear mechanisms of both a-C:Cr films in simulated body fluids are the slight polishing. • Both a-C:Cr films can greatly enhance the cytocompatibility of the original CoCrMo substrate. [ABSTRACT FROM AUTHOR]

Cr-doped graphite-like carbon (Cr-GLC) coatings and Cr-doped diamond-like carbon (Cr-DLC) coatings were prepared by PVD and PECVD, respectively. The lubrication behaviour of the solid-liquid composite lubrication systems was investigated using two ionic liquids (ILs) as lubricants. The results show that the friction coefficient was reduced by approximately 40% compared with that under the dry condition, and the composite system exhibited a good synergistic lubrication effect. The Cr-DLC coating showed better tribological behaviour than the Cr-GLC coating, which can be ascribed to a better physicochemical film formation under friction and the compact microstructure of the Cr-DLC coating. The synergistic effect of the composite systems was affected by the viscosity and corrosiveness of the ILs and the microstructure of the coatings. Image 1 • The Cr-GLC and Cr-DLC coatings were prepared by PVD and PECVD method, respectively. • The friction coefficient decreases from 0.11 (dry condition) to 0.045–0.06 (ILs condition). • The lubrication of solid-liquid systems is mainly affected by the wettability of ionic liquids. • The tribological properties of Cr-GLC in ionic liquids are more affected by the corrosion effect. [ABSTRACT FROM AUTHOR]