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This work is to deposit (CrNbTiAlV)CN/MoN coatings by alternating sputtering with multiple targets. The hardness and elastic modulus of the (CrNbTiAlV)CN/MoN multilayer coatings gradually increase with the decreasing of the modulation period from 420 to 110 nm; however, the values decrease on the multilayer coating with a modulation period of 50 nm. As the modulation period decreases, the characteristic of MoO3 debris changes from large flakes to smooth transfer tribolayers and then to small particles. The coating with a modulation period of 110 nm has a minimum friction coefficient and wear rate of about 0.11 and 4.4 × 10–6 mm3/(N m) at 500°C, respectively. This can be attributed to the fact that it has the best resistance to plastic deformation and tends to form smooth transfer tribolayers. [ABSTRACT FROM AUTHOR]

Macroscale superlubricity on engineering steel surfaces offers a promising solution for minimizing friction and wear in engineering applications. However, achieving superlubricity typically requires a long running‐in period, which may result in significant wear for the friction pair. Herein, a new lubricant with superlubricating properties is rationally designed by using polyethylene glycol (PEG) and critic acid (CA) under complexing effect with a running‐in period of about 800 s. Importantly, the introduction of carbon quantum dots (CQDs) obtained from the pyrolysis of CA into PEG aqueous solution shortens the running‐in period for achieving macroscale superlubricity (µ ≈ 0.005) between steel/steel contact to 44 s. The corresponding wear rate (1.15 × 10−7 mm3 N−1 m−1) on the steel disk is reduced by 77% due to the shorter running‐in time. Furthermore, the surface analysis combined with the molecular dynamics simulations demonstrates that CQDs easily adsorb on the surface of the friction pair, forming a carbon film that reduces interaction energy between the lubricant molecules and the substrate. This work provides new insights into the lubrication mechanism of CQDs and contributes to the design of liquid superlubricants with short running‐in periods and low wear rates on engineering steel surfaces. [ABSTRACT FROM AUTHOR]

The Mo x N coatings are deposited by direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS). It is found that the Mo x N coatings prepared by HiPIMS has a denser microstructure, higher hardness and wear resistance. Besides, the effect of peak current is investigated with respect to the microstructure, mechanical properties and tribological behavior of the coatings. As the peak current increases, the cross-sectional morphology of the coating transforms from featureless to columnar morphology, and the preferred orientation of the coating gradually transfers from (111) to (200). However, the hardness of the coating is not significantly influenced by the peak current. The Mo x N coating with a peak current of 260 A owns a low friction coefficient of 0.28, which is better than that of the Mo x N coating prepared by DCMS. The Mo x N coating with a peak current of 300 A provides excellent wear resistance with the lowest wear rate of 5 × 10−8 mm3/(Nm). [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]

WS 2 films with different structures and space lubricating oils are combined to construct the WS 2 /oils composite lubricating systems. Friction and wear of the WS 2 /oils systems are mainly studied in vacuum. Results show that WS 2 /P201 systems display much lower friction coefficient (μ ≈ 0.06) than WS 2 /PFPE systems (μ ≈ 0.11), which is found to depend on lubricity of oils. Noteworthily, the dense WS 2 film of the WS 2 /PFPE systems has the lowest wear rate of about 5.6 × 10−6 mm3·(N·m)−1 although friction coefficient of the system is high. This is due to good wettability of PFPE on the dense WS 2 film, whose contact angle is low to 5°. Eventually, the lubricating mechanism of the WS 2 /oil systems are revealed via correlating interaction between oil molecules and WS 2 crystals. [ABSTRACT FROM AUTHOR]

(CrNbTiAlV)N x high-entropy nitride films were prepared using magnetron sputtering method. The effect of substrate bias on the microstructure, mechanical, electrochemical, and tribo-corrosion properties of the films was systematically studied. The results show that the microstructure of the film changes from a loose columnar structure to a compact nanocrystal structure with the increase of substrate bias, accompanied by the preferred orientation from (200) to (111). The hardness, modulus and residual stress are positively correlated with increased substrate bias, reaching the maximum values of 35.3 GPa, 353.7 GPa and −6.41 GPa at −156 V, respectively. Under static corrosion, the film deposited under −126 V has the most positive E corr of −0.05 V and the lowest i corr of 0.013 μA/cm2. Under tribo-corrosion, the films deposited at −96 V and −126 V show the lowest coefficient of friction (~0.2) and wear rate (~4.4 × 10−7 mm3·N−1·m−1), respectively. The evolution of microstructure and mechanical property are the main factors affecting the tribo-corrosion behavior of (CrNbTiAlV)N x films. [Display omitted] • (CrNbTiAlV)N x high-entropy films were deposited at various substrate bias by magnetron sputtering. • The structure of the films changed from loose columnar to compact with the increase of substrate bias. • The hardness, modulus and residual stress of the films were positively correlated with increasing bias. • The influencing factors of (CrNbTiAlV)N x films under static corrosion and dynamic tribocorrosion were discussed. [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]