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Purpose: This study aims to investigate the effect of V doping on the microstructure, chemical stability, mechanical and vacuum tribological behavior of sputtered MoS2 coatings. Design/methodology/approach: The MoS2-V coatings are fabricated via tuning V target current by magnetron sputtering technique. The structural characteristic and elemental content of the coatings are measured by field emission scanning electron microscopy, X-ray diffractometer, electron probe X-ray micro-analyzer, Raman, X-ray photoelectron spectroscopy, high resolution transmission electron microscope and energy dispersive spectrometer. The hardness of the deposited coatings are tested by a nanoindentation technique. The vacuum tribological properties of MoS2-V coatings are studied by a ball-on-disc tribometer. Findings: Introducing V into the MoS2 coatings results in a more compact microstructure. The hardness of the coatings increases with the doping of V. The MoS2-V coating deposited at a current of 0.2 A obtains the lowest friction coefficient (0.043) under vacuum. As the amount of V doping increases, the wear rate of the coating decreases first and then increases, among which the coating deposited at a current of 0.5 A has the lowest wear rate of 2.2 × 10–6 mm3/N·m. Originality/value: This work elucidates the role of V doping on the lubrication mechanism of MoS2 coatings in a vacuum environment, and the MoS2-V coating is expected to be applied as a solid lubricant in space environment. [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]

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]

Abstract Coating oxidation performance is a major concern in modern machining and other high temperature applications. This study presents TiAlCrN composite coatings with different Cr content prepared on a magnetron sputtering device. SEM, AFM and XRD were used to determine the structure of the coatings. It was found that the coatings show a solid solution of B1-NaCl face-centered cubic structure with [200] preferential orientation. As the Cr content increases, the particle size and roughness of the coating increase slightly, while the hardness of the coating decreases. Oxidation tests revealed that no significant oxidation occurs in all coatings below 800 °C. However, as the oxidation temperature increases to 1000 °C, the Ti 0.32 Al 0.38 Cr 0.30 N coating undergoes severe oxidation and the Ti 0.17 Al 0.19 Cr 0.64 N coating remains good. The oxide scale of the coatings after oxidation test is analysis by XPS depth profiling in details. XPS results revealed that the oxide scale of the Ti 0.32 Al 0.38 Cr 0.30 N coating changes from a dense Al rich oxide layer (800 °C) to a loose and discontinuous Ti Al rich oxide layer (1000 °C), which is the main reason for its poor oxidation resistance. However, the Ti 0.17 Al 0.19 Cr 0.64 N coating shows a top loose Ti Al rich oxide layer and a dense bottom Cr Al rich oxide layer. The presence of this dense and continuous Cr Al rich oxide layer can limit the rapid diffusion of Ti atoms to the surface while preventing the oxygen atoms from diffusing into the interior, which is the key to excellent oxidation resistance of the Ti 0.17 Al 0.19 Cr 0.64 N coatings. Highlights • The oxide scale of TiAlCrN coating was characterized by XPS depth profiling. • As the chromium content increases, the oxidation resistance of the TiAlCrN coating increases. • The excellent oxidation resistance strongly depended on the compact Cr Al rich oxide layer. • The presence of the Cr Al rich oxide layer can limit the rapid diffusion of Ti atoms to the surface. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides are well known for their outstanding lubricating property. The special one of the family members, metallic NbSe 2 film, was deposited by sputtering in this study. The microstructure, electrical conductivity and tribological properties of NbSe 2 films were investigated by energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), grazing incidence X-ray diffraction (GIXRD), high resolution transmission electron microscopy (HRTEM), four-probe meter and ball-on-disk tribometer. The results showed that the microstructure of NbSe 2 film could be tailored by simply controlling the sputtering power. The suitable power of 180 W promoted to crystal growth of NbSe 2 film with edge plane orientation and formation of columnar structure, which possessed low static contact electrical resistivity and good adhesive strength on steel substrate. Both the dense and loose films made by lower and higher power, respectively, exhibited the downtrend of contact electroconductive and lubricative properties. The mechanism was discussed in terms of densification and crystallinity of films and transfer film formed on counterpart surface after sliding friction process. This novel NbSe 2 film with low friction and dynamic contact electrical resistance behaviors was expected to a more feasible candidate for lubricative and electroconductive bifunctional material application. [ABSTRACT FROM AUTHOR]

Adhesive wear is one of the major reasons for the failure of components during various tribological application, especially for rubbing with viscous materials. This study presents CrN/DLC/Cr-DLC multilayer composite coatings prepared on a plasma enhanced chemical vapor deposition (PECVD) device with the close field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique. SEM, XRD and Raman spectroscopy were used to determine the structure of multilayer coatings. It was found that the multilayer coatings are composed by the alternating CrN and DLC layers. Compared with the single CrN coatings, the friction coefficient of the CrN/DLC/Cr-DLC multilayer coating decreases about more than seven times after sliding a distance of 500 m. This helps to reduce the adhesive wear of multilayer coatings. Compared with the single CrN and DLC coating, the wear rate of the CrN/DLC/Cr-DLC multilayer coating is reduced by an order of magnitude to 7.10 × 10 −17 (sliding with AISI 440C) and 2.64 × 10 −17 (sliding with TC4) m 3 /(N m). The improved tribological performance of multilayer coatings mainly attributes to the introduction of lubricant DLC and hard support CrN layers, the enhancement of crack propagation inhibition, and the increment of elastic recovery value W e (71.49%) by multilayer design method. [ABSTRACT FROM AUTHOR]

Fracture toughness is an important characteristic for coatings for high speed cutting of titanium. This study focuses on improving the fracture toughness of the coatings using a layered design method. TiAlN/CrN multilayer coatings with bilayer periods between 12 nm and 270 nm were prepared by reactive magnetron sputtering. XRD results show the multilayer coatings have face-centred cubic structures. When the bilayer period of multilayer coating decreases from 270 nm to 25 nm, the coating hardness decreases from 24.5 GPa to 18.1 GPa. Increased fracture toughness and adhesion strength of multilayer coatings are observed with decreasing bilayer periods. A maximum fracture toughness (K IC ) of 3.6 MPa m 1/2 and adhesion strength of 107 N were obtained with a 25 nm bilayer period. The inhibition of crack propagation is the main reason for the high fracture toughness values in multilayer coatings. However, when the bilayer period is decreased further (12 nm), the coating hardness begins to increase rapidly to 23.4 GPa, and the fracture toughness and adhesion strength begin to decrease. Titanium cutting results show that an improvement in cutting performance is obtained with a TiAlN/CrN_25 multilayer coating. [ABSTRACT FROM AUTHOR]

High surface quality coatings play an important role in producing high precision coating tools for micromachining. This study focuses on the improvement of the coating surface quality by layered design method. The layered TiAlTaN/Ta coatings have been prepared by magnetron sputtering. SEM and AFM results revealed that the continuous growth of the columnar TiAlTaN crystals can be interrupted by layered design. The columnar crystal size of TiAlTaN coating decreased with the decreasing bilayer thickness. The coating surface roughness also gradually decreased from 36.6 ± 1.2 to 11.54 ± 0.6 to 8.9 ± 0.1 nm. Nanoidentation results showed an increasing coating hardness from 16 GPa to 20 GPa with decreasing bilayer thickness. Friction and wear test revealed that the coating friction coefficient increases from 0.70 to 0.93, then decreases to 0.62 with decreasing bilayer thickness. The layered method can improve mechanical and friction properties, meanwhile reducing surface roughness, which makes it a potentially promising method for fabricating high precision micromachining coating tools. [ABSTRACT FROM AUTHOR]

Adhesive wear is one of the major reasons for short tool life during machining titanium alloys. This study presents a new kind of low adhesive wear TaO functional coating prepared by magnetron sputtering. The composite coating is composed by two layers of a solid solution TiAlTaN in bottom and a TaO (Ta 2 O 5 or TaO x ) on top. Tool life of the TiAlTaN/TaO coatings is increased more than triple the TiAlTaN single coating by titanium cutting experiments. Cutting performance of commercial TiAlN-based coated tool is increased 267% after coating the TaO on the surface. Friction and wear between the coatings and Ti6Al4V counterpart have been conducted. The results show that both the friction coefficient of the coatings (from 1.05 to 0.82) and surface roughness (from 12.2 ± 0.6 to 7.1 ± 0.1 nm) are decreased by increasing TaO thickness from 0 to 150 nm. The adhesive bonds between coating and titanium also reduce with increasing the TaO thickness. This leads to the significantly reduction of the adhesion at the cutting tool tip after coated the TaO coating. This is because that the titanium is not easy to bind with the TaO coating by the calculated positive interaction energy between the Ta 2 O 5 surface and pure Ti. [ABSTRACT FROM AUTHOR]

Phase transformation between bcc and fcc in Fe–Ni nanoparticle has been studied by using molecular dynamics simulation with an embedded atom method. The transformation has been explored by designing the nanoparticles with different initial structures, sizes and elemental distributions at various Ni concentrations. The results show that the structural transformation is strongly related to the Ni content and elemental distribution. Initial fcc structure transforms to bcc for a lower Ni content and bcc transforms to fcc for a higher Ni content. The transformation is accompanied with a sharp reduction in energy even for the nanoparticle with a large size. Furthermore, lattice distortion first occurs before the transformation. The transformation from fcc to bcc is occurred by elongating fcc (100) to bcc (110) and that from bcc to fcc by compressing bcc (110) to fcc (100). The reason is that the nanoparticle has a low energy state for bcc structure with a lower Ni content and also for fcc structure with a higher Ni content. The coexistence of bcc and fcc phases appears with the change of elemental distribution. [ABSTRACT FROM AUTHOR]

Ti 1 − x − y Al x Ta y N coatings with various Ta contents ( y = 0.00–0.37) have been prepared by magnetron sputtering. Scanning electronic microscopy results show that the increased Ta content makes Ti 1 − x − y Al x Ta y N coatings more compact and exhibit a finer columnar structure. X-ray diffraction results show that the preferred orientation of Ti 1 − x − y Al x Ta y N coatings changes from (111) to (200) with increasing Ta content. Nanoindention results indicate that the hardness of the coatings sharply increases from 11 GPa without Ta to 31.2 GPa at y = 0.21. Solution strengthening caused by doping Ta is the main reason for the rapid increase of hardness. After oxidation in ambient air, Ti 0·44 Al 0.56 N coating is fully oxidized to α-TiO 2 and γ-TiO 2 at 600 °C. A significant increase of oxidation resistance for Ti 0·37 Al 0.42 Ta 0.21 N coating has been observed at 800 °C. However, a higher Ta content ( y = 0.37) is not conducive to retard the formation of α-TiO 2 phase at low temperature, but will increase lattice distortion. This can make the coating easy to spall during further oxidation. [ABSTRACT FROM AUTHOR]

a-C:H films were produced on 316 L stainless steel via magnetron sputtering technique. The effects of bias voltage on the composition, structure and properties of the films were studied. The sp2C fraction grows as the bias voltage increases, and the internal stress and hardness increase constantly. In ambient air, the films deposited at − 150 V have the lowest friction coefficient (COF) of 0.095, while those at − 30 V have the lowest COF of 0.028 in salt solution, benefiting from the higher H content. The corrosion resistance of the film is affected comprehensively by the thickness, surface morphology, sp2 clusters and transition layer. The a-C:H film at − 60 V has the lowest corrosion current density (5.41 ×10−11 A/cm2) and the highest protection efficiency (99.8 %). • The microstructure and composition of the a-C:H films were tailored by the bias. • The lowest friction coefficient in ambient air was 0.095 at the bias of − 150 V. • The lowest average friction coefficient in saline environment was 0.028 at − 30 V. • The anti-corrosion protection efficiency of the 316 L substrate achieved 99.8 % at − 60 V. [ABSTRACT FROM AUTHOR]

Research on the relationship of microstructure and properties of coated tools such as TiAlN and TiAlSiN plays a key role in obtaining the needed cutting performance in titanium machining. In this study, three kinds of coatings of TiAlN, TiAlSiN monolayer and TiAlN/TiAlSiN composite multilayer have been fabricated by magnetron sputtering method. It is found that the coating structure changes from columnar growth to nanocrystal growth by doping Si element. The TiAlN/TiAlSiN coating is composed by a coarse columnar TiAlN bottom layer and a fine nanocrystalline TiAlSiN top layer. Premature spalling problem (Lc2) is improved by forming the TiAlN/TiAlSiN multilayer structure. Titanium cutting experiment shows that the major wear mechanism of these coated tools is adhesive wear and chipping. The TiAlSiN coated tool has the longest cutting distance at various cutting speeds in these three kinds of coatings. This is because less built-up edge and chipping are generated at the cutting edge due to the dense nanocrystal structure, high hardness and good oxidation resistance of TiAlSiN coating. Therefore, the TiAlSiN coating with dense structure, high hardness and good oxidation resistance is recommended to use in high speed turning titanium. [ABSTRACT FROM AUTHOR]

Structural evolutions of Co 561 clusters supported on the Cu(010) substrate were studied by molecular dynamics simulation using an embedded atom method. Energy, snapshot, pair distribution function and epitaxial factor were used to analyze the effects of supported position, configuration and temperature on the structural evolutions. It is found that the energy of the cluster changes significantly with varying the supported position and the original configuration. The most stable supported position is (111) facet. As a function of configuration the stability decreases in the order: icosahedron > truncated octahedron > decahedron > cuboctahedron > sphere. Supported (111) facet changes to stack along the (100) of substrate. Epitaxial growth on the substrate occurs for all configurations. The epitaxial temperature and the amount of epitaxial atoms are related to the configuration. The epitaxial growth is adverse to the stability of the cluster, while the epitaxy has no effect on the crystal structure of the supported cluster. The energy of the cluster is reduced by the epitaxial growth and atomic penetration into the substrate but is enhanced by the distortion of the cluster on the substrate. [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]

[Display omitted] • The nanostructure of a-Si:H interlayer can be tailored by bias power. • Nanoporous interlayer transforms into clusters and then network with increasing bias. • The crosslinked network results in the highest adhesion and the lowest stress. • The tiny clusters weaken the lattice mismatch and reduce the Si-Fe bonds. Different nanostructures of the a-Si:H interlayer were designed by tuning the bias power to reveal the impacts on the adhesion of thick DLC coatings prepared by PECVD. Besides the formation of stable Si-Fe bonds, the a-Si:H interlayer transformed from nano-porous structure into tiny clusters and finally into crosslinked network by raising the bias power from 125 to 425 W. The interlayer with crosslinked network promoted the formation of more Fe-Si dangling bonds at the bonding layer as well as better structure matching with top layers, resulting in the highest adhesion strength of 32 N and the lowest internal compressive stress of −1.44 GPa. When amounts of tiny clusters were formed in the interlayer at 275 W, the lowest adhesion strength of 23.5 N was obtained. This was due to the low chemical reactivity of tiny clusters hindered the formation of the Si-Fe bonds. [ABSTRACT FROM AUTHOR]

To improve the adaptability of GLC coatings in aqueous environment, a dense structure for GLC coatings was designed and constructed by nitrogen doping via PVD technique. The nitrogen content was tailored via tuning the nitrogen flow rate to optimize the tribological performances of the N-doped GLC coatings in water as well as to investigate the effects of different nitrogen contents. And the optimal nitrogen flow rate was 5 sccm. The results implied the nitrogen doping favored the increase of adhesion strength. The dense structure built by nitrogen doping entitled the N-GLC coatings to improved wear resistance in water and enhanced aqueous-adaptability, because the corrosion by water can be effectively inhibited compared with the column-structured nitrogen-free GLC coatings via PVD. [Display omitted] • The nitrogen modified GLC coatings with dense structure and better adhesion strength were constructed via PVD technique. • The nitrogen contents in the N-doped GLC coatings can be tailored by tuning the nitrogen flow rate in the PVD process. • The nitrogen-free GLC coating was failed in water environment, while the N-GLC coating with 5 sccm flow rate showed a lowest wear rate of 2.47 × 10-8 mm3/Nm. • The nitrogen doping contributed to the densification of the coatings and thus improved their aqueous-adaptability. [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]

High-entropy carbonitrides exhibit excellent properties in friction and corrosion. Here, the tribo-corrosion response of (CrNbTiAlV)C x N y coating were studied in 3.5 wt.% NaCl solution at room temperature. The doping of carbon makes the coating structure dense. When the carbon content of the coating is 40%, the coating exhibits maximum hardness (20.21 GPa). As the carbon content increases, the synergistic effect of tribo-corrosion on the coating gradually weakens, and friction coefficient decreases. The coating with 40% carbon content has the smallest change in static and dynamic current density (0.14 ×10−8 A/cm2), the smallest friction coefficient (0.28), and the smallest wear volume loss. These results show that the coating can effectively protect the substrate in case of tribo-corrosion. [ABSTRACT FROM AUTHOR]

(CrNbTiAlVMo) x N 1−x coatings were deposited on 316 L steel by sputtering method. The structure, mechanical and tribo-corrosion performances of the coating were studied. The results show that all coatings exhibit single FCC structure. With the increase of Mo content, the surface particle size increases, and the orientation changes from (111) to (200). The maximum hardness reaches 44.3 GPa and the corresponding elastic modulus is 405 GPa. Tribo-corrosion test show that the coatings exhibit better resistance to tribo-corrosion than 316 L steel. The coating with 8 at% Mo content has the lowest static current density (7.49 ×10−9 A/cm2) and dynamic current density (9.33 ×10−8 A/cm2), while the coating with 32 at% Mo content shows the smallest wear volume. The related synergistic mechanism of tribo-corrosion was discussed. • The (CrNbTiAlVMo)xN1-x coatings with different Mo contents were prepared by magnetron sputtering. • When the Mo content is 8%, the coating exhibits the highest hardness (44.3 GPa) and elastic modulus (405 GPa). • The (CrNbTiAlVMo)xN1-x coatings exhibit better resistance to tribo-corrosion than 316 L steel. [ABSTRACT FROM AUTHOR]

The (CrAlTiNbV)N x coatings are fabricated by controlling the substrate bias via magnetron sputtering method. Under low substrate bias, the coating tends to form a loose columnar crystal structure with (200) preferred orientation. However, when the substrate bias increases, the coating transforms into a dense nanocrystalline structure, and the (111) orientation is enhanced. As the substrate bias increases, the residual stress and hardness of the coating gradually increase, while the adhesion strength decreases slightly. Friction tests show that the coating possesses the lowest average friction coefficient (about 0.06) and wear rate (8.7 × 10-9 mm3/N·m) in 4050# aviation lubricant, which is achieved under the substrate bias of -96 V and -126 V, respectively. [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]

The preparation and investigation of lead-free bronze solid-lubricating coating is of great significance for the protection of moving parts in seawater condition. In this work, the (Cu-5Sn)/Al 2 O 3 -Ag solid-lubricating coating was prepared by low-pressure cold spray (LPCS) technology. The influence of the Ag content (0–20 wt%) in feedstocks on the microstructure, deposition efficiency and mechanical properties of the coatings was investigated. Meanwhile, the tribological behavior of the coatings in artificial seawater environment was examined. The results showed that the Al 2 O 3 particles contribute to the densified microstructure and the increased Ag content in powders improved the deposition efficiency of the coatings, but inferior hardness. The satisfactory bonding strength between the coating and substrate was achieved. In artificial seawater condition, the friction coefficient of the coatings decreased with the increase of the Ag content in the coatings. However, more Ag will sacrifice the anti-wear property of the coatings. The wear mechanisms of the coatings were abrasive and corrosive wear. • The (Cu-5Sn)/Al 2 O 3 -Ag solid-lubricating coating was deposited by low-pressure cold spraying. • With the increase of Ag content in feedstock, the deposition efficiency of the coating increased. • The coating possesses a satisfactory bonding strength with the AA 7075-T651 substrate. • The coating has the low friction coefficient and high wear resistance in seawater condition. [ABSTRACT FROM AUTHOR]

Electrodeposited ZnO films have been annealed at 300 °C for 2 h under 12 T high magnetic field (HMF) with the directions of parallel and perpendicular to the films, respectively. The structural, optical and electric properties were characterized by scanning electron microscopy, X-ray diffraction, photoluminescence (PL) spectra, X-ray photoemission spectroscopy (XPS) and Seebeck coefficient/electrical resistance measuring system. The results show that HMF has a significant effect on the growth of ZnO films along c -axis and leads to hexagonal platelets of ZnO growing parallel to the direction of HMF. Furthermore, the hexagonal platelets become bulky platelets with an obvious trendy rotating their c -axis parallel to the substrate. The PL spectra of all the films exhibits the UV and blue emission, moreover, the blue emission plays the main role. The resistivity of ZnO films increases with the increase of measure temperature, which shows a typical degenerate semiconductor characteristic. HMF reduces significantly the intensity of whole emission peaks and the resistivity of ZnO films. These may be attribute to the significant changes of the structure and morphology of ZnO films, leading to various amounts of the defects in the ZnO crystal. [ABSTRACT FROM AUTHOR]

High temperature coatings possess great potential for improving operation temperature of 4th generation nuclear reactor. In this paper, a high-entropy alloy nitride coatings (CrAlTiNbV)N x were investigated for the application in corrosive lead-bismuth alloy (LBE). The coatings were synthesized by unbalanced magnetron sputtering on ferritic/martensitic (F/M) steel. Properties of (CrAlTiNbV)N x are systematically investigated from perspective of the electron structure, crystalline, and mechanical properties under different bias voltage applied on samples. Significant improvement of hardness (30 GPa) is obtained at bias voltage of -156 V. Furthermore, the corrosion behavior in 550 °C lead bismuth eutectic (LBE) was conducted for 1200 h with saturated oxygen content, which demonstrates the dense structure of coatings with no obvious crack, spallation that characterized by the SEM, EDS, and TEM. Upon the application of high bias voltage, more prone formation of high-density grain boundary with fine grains extends the diffusion path of Pb and Bi are achieved for excellent LBE corrosion resistance. Our work not only provide an insight to the electron structure of high entropy alloy nitrides, but also shows a potential application for (CrAlTiNbV)N x protecting fuel cladding in the next generation lead based reactor. [ABSTRACT FROM AUTHOR]

This paper studies the effects of Ag atomic segregation from the inner (100) or (111) planes on the melting of Ag-Pd clusters with different sizes by a molecular dynamics simulation. The results show that Ag segregation leads to the atomic energy decreases with increasing the temperature. Furthermore, the effect of the (100) segregation is larger than that of the (111) segregation. Meanwhile, the influence of segregation on the energy decreases with increasing the cluster size. The melting points of the clusters without segregation are the largest, followed by the clusters with a (111) and (100) segregation. [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]

[Display omitted] • The (CrAlTiNbV)N x high-entropy coatings are prepared by magnetron sputtering method. • All coatings exhibit columnar growth morphology and own a single FCC structure. • The S-38 owns a friction coefficient of 0.096 and wear rate of 1.8 × 10−7 mm3/(N·m). • The excellent wear resistance of S-38 is mainly attributed to its dense structure. (CrAlTiNbV)N x high-entropy nitride coatings are deposited via tuning nitrogen flow rates, and evaluating their influence on the microstructure, mechanical and tribological properties of the coatings. All deposited coatings exhibit columnar growth morphology and own a single face-center-cubic structure. As the nitrogen flow rate increases, the preferred orientation of the coating gradually transfers from (1 1 1) to (2 0 0) and (2 2 0), and then changes back to (1 1 1) with the nitrogen flow rate continues to increase. The S-38 sample possesses the optimal plastic deformation resistance and adhesion strength. Friction and wear results show that the (CrAlTiNbV)N x coating deposited at nitrogen flow rate of 38 sccm owns the best tribological properties with a friction coefficient of 0.096 and wear rate of 1.8 × 10−7 mm3/(N·m) in 4050# aviation oil. [ABSTRACT FROM AUTHOR]

The wear-resistant Ta 4 HfC 5 nanoceramics were prepared via polymer preceramic routes. Tribological behavior of the generated nanoceramics from room temperature to elevated temperatures was investigated. The results shows that the coefficient of friction (COF) of the Ta 4 HfC 5 sliding against Si 3 N 4 first increases and then decreases with the rise of temperature, reaching as low as about 0.20 at 800 °C. The low COF at 800 °C is dominantly ascribed to the formation of oxide tribo-film on the worn surface. The fine microstructure benefiting from the polymer precursor synthesis imposes positive effect to the reduction of friction coefficient at the high temperature. • Ta 4 HfC 5 nanoceramics with fine microstructure was prepared by polymer-derived ceramics (PDCs) route. • The high temperature tribological behavior of the Ta 4 HfC 5 nanoceramics was investigated. • The low friction coefficient of the polymer-derived Ta 4 HfC 5 nanoceramics reached as low as about 0.20 at 800 °C. • The fine microstructure of polymer-derived Ta 4 HfC 5 contributed to the formation of compact oxide tribo-layer at 800 °C. [ABSTRACT FROM AUTHOR]

The high-throughput preparation of MoS 2 -(Cr, Nb, Ti, Al, V) composite coatings was achieved by multi-targets co-sputtering method. Based on the obtained friction coefficient of 236 samples as the criterion, four samples with the largest difference in friction coefficient were screened out for further detailed investigations. The results demonstrated that high metal doping amount can dense the coating and reduce the particle size. As the doping content increased, the coating transformed from nanocrystalline to amorphous structure. Consequently, MoS 2 -(Cr, Nb, Ti, Al, V) composite coatings with high doping levels presented higher hardness and better atmospheric tribological properties. Moreover, the Cr and Al dopants can better inhibit the oxidation of MoS 2 than Nb, Ti and V dopants owing to the denser oxide films. • More than two hundreds of doped MoS 2 coatings are prepared by high throughput preparation. • The coatings with high doping contents own higher hardness and better tribological properties. • As the doping content increases, the coating transform from nanocrystalline to amorphous structure. • The Cr and Al dopants can better inhibit the oxidation of MoS 2 than Nb, Ti and V dopants. • The P8 sample owns a friction coefficient of about 0.03 and wear rate of 3.16 × 10−7 mm3/(N.•m). [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]