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Silicon and oxygen-doped hydrogenated amorphous carbon (a -C:H:Si:O), typically termed as diamond-like nanocomposite (DLN), is amongst the most widely adapted coating materials for advanced applications. Traditionally, these coatings are deposited by plasma-enhanced chemical vapor deposition (PECVD) using organosilicon precursors, which not only restrict coating stoichiometry but also have a high environmental footprint. Here, we report the deposition of highly dense and microscopically defect-free a -C:H:Si:O coating using magnetron sputtering as a facile and sustainable deposition method that allows a fine stoichiometry control. Furthermore, we investigate the evolution of the atomic structure and the local-atomic environment when Si, O, and H atoms are successively doped into the amorphous carbon (a -C) matrix. Diffraction and spectroscopic analyses of doped coatings indicate the absence of any long-range order and an atomic-scale composite structure. The results also establish that doping of a -C leads to improved sp 3 bonding, formation of Si–O-based networks, and termination of carbon dangling bonds, resulting in increased structural stability. The densification of the coating, combined with improved sp 3 character, results in hardness and modulus exceeding those of PECVD-deposited coatings. These findings present a viable potential of magnetron sputtering as a straightforward and greener alternative to traditional PECVD-based methods for producing a promising coating material. [Display omitted] • A facile and sustainable PVD method for a -C:H:Si:O coating is reported. • Structural evolution as triggered by Si, O, and H dopants is elucidated. • This method yields defect-free coatings with high density (2.5 g cm−3) and sp 3 bond fraction (∼0.66). • Hardness (24.4 GPa) and reduced modulus (212.9 GPa) for a -C:H:Si:O reporterd herein, surpass that of PECVD deposited coatings. [ABSTRACT FROM AUTHOR]

Novel multilayered films were engineered by integrating W 2 N and Ag-SiN x layers in a multilayer structure to obtain improved hardness and tribological properties. The films were fabricated by alternating magnetron sputtering, depositing 40 nm layers of W 2 N with varying thickness of Ag-SiN x layers varying in thickness from 4 to 20 nm. The effect of the increase thickness of the Ag-SiN x layers in the films microstructure and tribological properties were accessed. Tribological experiments were conducted at room temperature (RT), 500 °C, and RT-500 °C cycling conditions. The results revealed the production of a multilayered structure comprising single fcc-W 2 N layers interspersed with dual-phase layers consisting of fcc-Ag and amorphous SiN x phases. Tribological results indicated an improvement in the tribological performance with increase thickness of the Ag-SiN x layer up to 12 nm. The tribo-synergistic/combined action of both W 2 N and Ag-SiN x layers, along with the presence of layered lubricant tribo-phases of WO 3 and Ag 2 WO 4 , showcased the pivot role in reducing friction and enhancing wear resistance. The optimized multilayered film, featuring a 12 nm Ag-SiN x layer, demonstrated exceptional tribological properties under temperature-cycling from RT to 500 °C. [Display omitted] [ABSTRACT FROM AUTHOR]

Two sets of nanoscale multilayer Ti-DLC/DLC coatings, with similar chemical composition but different periods between consecutive layers (0.4 and 5.5 nm), were deposited by non-reactive direct current magnetron sputtering using different rotational speeds of the substrate holder (12 and 1 rpm, respectively) in this work. The results show that the overall Ti content in the coatings varied from ≈ 2.9 to ≈ 8.2 at. % in both cases. Significant fluctuations in the Ti concentration between the middle points of the DLC and Ti-DLC layers were observed for the coatings deposited at 1 rpm. All the coatings deposited were mainly amorphous, presenting a columnar structure and a cauliflower-like granular surface morphology. The sp2/sp3 ratio increased as the concentration of Ti rose. The coatings deposited at 1 rpm demonstrated better mechanical properties (up to 33 % improvement in hardness and up to 25 % improvement in the elastic modulus) when compared to the equivalent coatings deposited at 12 rpm. The multilayer titanium doped coating (deposited at 1 rpm) with 5.9 at. % Ti presented the most significant improvement in mechanical properties when compared to pure DLC and monolayer coatings deposited at 12 rpm. The results confirmed that it is possible to tune the performance of this type of coatings by depositing alternating layers of pure DLC and Ti-doped DLC. [Display omitted] • Monolayer and multilayer Ti-doped DLC coatings were successfully deposited by DC magnetron sputtering. • Multilayer structure was achieved by controlling substrate holder rotational speed. • All the Ti-doped DLC coatings had higher values of adhesion than pure DLC. • Multilayer Ti-DLC coatings showed higher hardness and elastic modulus than monolayer coatings. • The period of the layers, chemical composition, and residual stresses affected the performance of the coatings. [ABSTRACT FROM AUTHOR]

Reduction of friction and wear at the sliding surfaces are the main concern in several applications. From an extensive list of low friction hard coatings, DLC type is one of the most studied and develop for achieving low wear and friction. The addition of an alloying element is extensively used, since it can change significantly the coatings performance. Therefore, in this research the tribological behaviour of DLC coatings alloyed with different elements was evaluated, since no works comparing the tribological properties of DLC films with approximately the same alloying elements concentration are reported in the literature. The coatings were deposited by physical vapor deposition and alloyed with: tungsten (W), silver (Ag), silicon (Si), silicon and oxygen (SiO), with concentrations of metallic elements between 10 and 15 at. % and a pure DLC coating was also deposited for comparison purposes. The coatings hardness varied between 23 GPa for the pure DLC and 11 GPa for the alloyed with Si and O. The tribological behaviour of the coatings was evaluated by pin-on-disk against 10 mm 100Cr6 steel balls, at room temperature (RT) and 100 °C. The best wear resistance was achieved with the pure DLC and DLC-W for RT tests. At RT the lowest friction was obtained with the DLCSi and DLCSiO coatings. Despite of the low COF values, those coatings displayed the highest specific wear rate values among all the films. This is attributed to the presence of hard SiC particles stick at the ball counterpart which promotes severe abrasion of the coatings surface. The increase of the temperature to 100 °C increases significantly the friction coefficient for the DLC and DLC-W coatings, whilst, for DLC-Ag, DLC-Si and DLC-SiO coatings a slight decrease is noticed. At this temperature DLCAg coating is the more performing due to the formation of a tick tribolayer rich in Ag adhered at the counterpart surface. With this work it was concluded that friction and wear are not directly related, and the third bodies formed on the sliding surfaces have major influence on the tribological performance of the system. • Diamond-like carbon (DLC) films were alloyed with different elements. • Alloying the DLC coatings decreases the Hardness and reduced Young Modulus. • Pin-on-disk tests were performed at two different temperatures against steel balls. • At RT the lowest friction (COF) was obtained for DLCSi and the highest with DLCW. • Increase the temperature results in a decrease of (COF) for DLCAg, DLCSi, DLCSiO. [ABSTRACT FROM AUTHOR]

The tribological processes still cause a significant increase in energy consumption worldwide. In this work, we deposited self-lubricating coatings for the purpose of reducing friction during sliding against rubber. One of the coatings was also treated with laser. We studied the morphological, structural and mechanical properties of the proposed solutions. Tribological tests were performed using a pin on disk device. The laser treatment improved the crystallinity of the WSx phase. This improvement was coupled with a reduction of the hardness in the laser-treated areas due to graphitization. The laser-treated sample showed a reduction in friction only during the initial stages of sliding. The lowest friction was observed during the testing of unalloyed sputtered WS x coating, but it suffered more wear. [Display omitted] [ABSTRACT FROM AUTHOR]

W–S–N self-lubricant coatings were deposited by d.c. reactive magnetron sputtering at two total discharge pressures of 0.6 and 1.2 Pa. The nitrogen content and S/W ratio varied from 0 to 30 at.%, and 0.6 to 1.6, respectively. The effect of deposition conditions on chemical composition, structure and mechanical properties was studied; coatings with the most promising properties have been selected for tribological testing. Coatings were nanostructured with nanograins of tungsten disulfide; the size of which decreased with increasing nitrogen content. Hardness increased with N content up to 7 GPa for coating deposited with a discharge pressure of 1.2 Pa; coatings deposited at lower pressure exhibited hardness around 9 GPa. Friction and wear behavior in humid air and dry nitrogen was evaluated using a pin-on-disk tribometer. The wear tracks and the ball wear scars were analyzed by Raman spectroscopy and scanning electron microscopy. Although the friction coefficient in dry nitrogen was significantly lower than in humid air, the wear rate was similar for both environments. Detailed wear track surface analysis showed that the tribolayer formed on the surface contained mostly tungsten disulfide and tungsten oxide. [ABSTRACT FROM AUTHOR]

ABSTRACT Carbon-based coatings with different W contents were deposited by direct current magnetron sputtering in reactive and non-reactive atmospheres. All deposited coatings have compact morphologies with amorphous (tungsten-free) or nanocrystalline structures (tungsten-doped). The latter one was indicated by very broad peaks in X-ray Diffraction spectra in the position of tungsten carbide suggesting W-carbide nanoparticles embedded in an amorphous carbon matrix. The hardness increased from 10 to 15 GPa with increasing W content. The coatings were tribological tested at dry and lubricated conditions with increasing temperature in a coating/steel configuration. In dry sliding, the friction coefficient increases with the increase of the temperature reaching values higher than 1.0. The friction is significantly lower in lubricated contact using three different oils: poly-alpha-olefin, paraffin and olive oil. The olive oil shows promising lubricating properties at the temperature lower than 70°C; however, at higher temperature, the coatings were quickly worn through. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Transition metal dichalcogenides (TMD) are well known for their self lubricant properties, due to unique crystal structure, with low hardness which makes them inappropriate in applications requiring high load bearing capacity. Nevertheless, there is still a considerable potential for further improvements since other TMDs such as diselenides remain almost unknown. The WSeC coatings were deposited by either co-sputtering from WSe2 and C targets or by working in reactive mode in an Ar+CH4 atmosphere. Carbon content varied from 25at.% up to 70at.%, Se/W ratio of co-sputtered coatings was between 0.9 and 1.0, with no significant influence of the carbon content on their variations, while in the reactive process it reached values higher than 1.7. The hardness of the coatings was evaluated by nanoindentation, with values between 1.6 and 5.6GPa. The structure of the coatings was analysed by X-ray diffraction in glancing mode, showing that the coatings have a quasi-amorphous structure. Finally, the selected samples were tested on pin-on-disc showing low friction properties of WSeC co-sputtered coatings. [Copyright &y& Elsevier]

We present a strategy to enhance the tribological performances of diamond-like carbon (DLC) films based on synergistic chemical modifications in the polymer lubricant additives and in the carbon film. Our experiments revealed that the polymer functionalization with nitrogen-containing groups and the DLC doping with silicon atoms result in significant friction and wear reduction under severe boundary lubrication conditions. Atomic Force Microscopy revealed the formation of a lubricious tribofilm. Ab initio calculations highlighted the key role of N-Si interactions in promoting the polymer chemisorption on the film, which represents the first, essential step for the tribofilm formation. Our findings suggest that targeted chemical modifications in lubricants and films can substantially advance the tribological performances of DLC films for various industrial applications. [Display omitted] • Nitrogen-functionalized copolymer and Si-doped DLC reduce friction and wear. • Formation of a lubricious tribofilm observed with Atomic Force Microscopy. • Ab initio simulations show DMAEMA forms N-Si bonds on Si-DLC surfaces. • N-Si interactions promote polymer chemisorption, crucial for tribofilm formation. [ABSTRACT FROM AUTHOR]

W–S–C thin films were deposited by magnetron sputtering in a semi-industrial deposition unit. Various parameters like the composition, crystallinity, morphology and hardness were studied. A single coating was selected for tribological studies in different testing environments. The tribological response during ambient air testing was governed mainly by carbon-based phase at low normal loads and both carbon-based and WS 2 rich tribofilms at higher loads. Very low coefficients of friction (~0.01) were obtained during testing at elevated temperature due to accelerated formation of WS 2 rich tribofilms. The tribological response in a vacuum against a steel-based counterbody was unsatisfactory due to the presence of a carbon-phase at the sliding interface. Discrepancies were observed between the tribological response in dry N 2 and vacuum environments. • Self-lubricant W–S–C coatings were deposited by magnetron sputtering in a semi-industrial unit. • The composition was affected by the target to substrate distance, the power applied to the targets and substrate bias. • Good tribological performance was observed during testing at RT and elevated temperatures up to 400 °C. • Coating both counterbodies can greatly improve the tribological performance in a vacuum environment. [ABSTRACT FROM AUTHOR]

Self-lubricant W-S-C coatings are good candidates for application on mechanical components subjected to dry sliding in diverse operating environments. One of the challenges during deposition of these coatings by magnetron sputtering is the compositional variations, mainly related to the S/W ratio, which can strongly affect the tribological performance. With this study we aim to demonstrate the importance of the location of the surfaces to be coated in the chamber during deposition of W-S-C coatings. The coatings were deposited on substrates placed at 4 different locations in order to mimic the surfaces of bigger components with more complex geometry like molds or dies. The chemical composition, microstructure and the mechano-tribological properties were studied by scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), nanoindentation, scratch testing and reciprocating pin-on-disk testing. The location of the substrate affected the chemical composition, with the difference being mainly a result of different level of bombardment with reflected Ar neutrals. The carbon content did not change significantly with values of ~50 at.%. Bigger differences were observed for the S/W ratio with values ranging between 1.2 and 1.7. The difference in the S/W ratio affected the mechano-tribological properties. An adaptive tribological behavior with low friction and wear during testing in ambient air, dry N 2 and at elevated temperature (200 °C) could be achieved for the coatings having a S/W ratio higher than 1.5. The placement of bigger components should carefully be considered for W-S-C coatings. The locations should yield coatings with S/W ratio of higher than 1.5 in order to have superior tribological performance. • Self-lubricant W-S-C coatings deposited by magnetron sputtering in a semi-industrial unit. • Exploration of the effect of the substrate location on the properties • The coatings have a nanocomposite structure • Adaptive tribological response for the coatings with S/W ratio higher than 1.5 [ABSTRACT FROM AUTHOR]

Achieving the stringent demands of sustainable tribological industrial applications poses a significant challenge, particular in optimizing the self-lubricant performance of nitride-based films. This paper tackled this challenge by designing and depositing a series of ZrN-MoSN composite films with varying (Mo + S)/Zr ratios, employing RF magnetron sputtering, aimed to enhance the tribological properties through utilizing the high loading capacity of the ZrN matrix and the exceptional self-lubricating attributes of Mo-S-N additives. After conducting thorough investigations on the microstructure, and tribological properties, the results revealed that the dense columnar structured ZrN-MoSN composite films displayed a polycrystalline composition comprising fcc-ZrN and hcp-MoS 2 phases, intertwined with amorphous phases of Mo(SN) x and MoS 2 (N 2). (Mo + S)/Zr ratios below 1.08 exhibited a minor impact on the room temperature (RT) tribological properties, while higher ratios led to degradation on RT average friction coefficient (COF) and wear rate (WR). However, the synergistic effect of ZrN matrix and the tribo-phases of layered MoO 3 and hard ZrO 2 contributed to the significant enhanced 500 °C tribological properties, particularly with an optimized (Mo + S)/Zr ratio of 0.43. [Display omitted] • ZrN-MoSN composite films were fabricated by the magnetron co-sputtering technique. • The films exhibited a coexistence of fcc-ZrN, hcp-MoS 2 , Mo(SN) x and MoS 2 (N 2) phases. • Incorporating Mo-S-N in ZrN notably bolstered the 500 °C tribological properties. [ABSTRACT FROM AUTHOR]

Carbon alloyed transition metal dichalcogenide (TMD) coatings have attracted attention in the field of tribology due to their ability to provide friction and wear reduction in diverse operating environments. This study is devoted to the up-scaling of the deposition process for self-lubricant molybdenum-selenium-carbon (Mo-Se-C) coatings. For this purpose, Mo-Se-C nanocomposite coatings are deposited by closed-field unbalanced magnetron sputtering in a semi-industrial deposition unit. The effect of the addition of carbon to sputtered MoSe x coatings, the usage of negative substrate bias, and the target-to-substrate distance are studied. The carbon addition significantly improves the compactness and the mechanical properties of the pure MoSe x coatings. An additional improvement is achieved by the usage of negative substrate bias during the deposition. The optimized coatings have featureless cross-sectional morphology and amorphous X-ray diffraction structure. Transmission electron microscopy reveals the presence of nanosized crystallites of MoSe 2 enclosed in an amorphous carbon matrix. The hardness, measured through nanoindentation, is ~7–8 GPa for the coatings having C content of ~50 at.%, and a compact morphology. The best tribological properties for reciprocating pin-on-disk testing are characterized by coefficients of friction of 0.08–0.09 in ambient air conditions and 0.04–0.06 in dry N 2 environment and elevated temperature (200 °C). The lowest specific wear rates were 2–3 × 10−7 mm3/Nm during sliding in ambient air and under dry N 2 , with higher values of 7–10 × 10−7 mm3/Nm during testing at elevated temperature. Mo-Se-C coatings can be upscaled for industrial production showing potential tribological properties for low friction applications. • Self-lubricant Mo-Se-C coatings were deposited by magnetron sputtering. • The target-to-substrate distance affected the Se/Mo ratio. • Usage of negative substrate bias improved the mechanical properties. • Good tribological properties were achieved during testing in different environments. [ABSTRACT FROM AUTHOR]

Mo-Se-C is a very less explored subset of carbon-based transition metal dichalcogenide (TMD-C) nanocomposite coatings but a potential candidate as solid lubricant coatings in aerospace and automotive industries due to excellent frictional stability both in humid air and vacuum conditions. The present work aims at the development and investigation of dc magnetron co-sputtered Mo-Se-C coatings using separate C and MoSe 2 targets, as a first step for industrial up-scaling. By varying the applied C power, a carbon content of 44 to 60 at. % was achieved. 50 at. % C was selected for the deposition of coatings with negative substrate bias of 50, 70 and 90 V dc voltage and, for the latter, pulsed dc bias was also applied. Maximum Se/Mo ratio of 1.88 was evaluated by wavelength dispersive spectroscopy (WDS) analysis. After the application of substrate bias, the deposition rate and Se/Mo ratio decreased while higher compactness was observed by scanning electron microscopy (SEM). Mo-Se-C coatings displayed broad amorphous grazing incidence X-ray diffraction patterns. Transmission electron microscopy (TEM) showed MoSe 2 platelets randomly oriented in amorphous carbon matrix. X-ray photoelectron spectroscopy (XPS) was not conclusive towards the presence of Mo-C bonds while Raman analysis showed the presence of MoSe 2 crystalline peaks. Nano-indentation tests showed an increase in the hardness of coatings deposited under negative substrate bias. Tribological tests were performed in humid air and dry nitrogen. 400C(90V) coating displayed the highest frictional stability in both environments, while the lowest friction coefficient of 0.025 and specific wear rate of 2.4 × 10-8 mm3/Nm were achieved for tests in dry nitrogen. • Effects of C power and application of substrate bias on the Mo-Se-C nanocomposite coatings deposited by DCMS were investigated. • Combination of MoSe 2 with C led to compactness, amorphousness and mechanical property enhancement as compared to pure MoSe 2 coatings. • Substrate bias resulted in highly compact and non-stochiometric coatings. • MoSe 2 nano-platelets were always present in amorphous C matrix, leading to excellent tribological properties. • Mo-Se-C coatings displayed promising compositional, structural, mechanical and sliding properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • First report on effect of carrier gas on nanoindentation responses of GaN Films. • New method to compute E and H as alternative to continuous stiffness measurement. • Derivation of nanomechanical and physical properties of GaN films. • Interpretation of the correlation between GaN growth modes and mechanical behavior. The effect of carrier gas on nanomechanical properties of GaN thin films grown on (0001) sapphire substrates by metal–organic chemical vapor deposition (MOCVD) process, was studied by Berkovich nanoindentation. GaN/H 2 and GaN/N 2 films were deposited using hydrogen and nitrogen, as carrier gases, respectively. New method was developed to compute the contact stiffness versus the penetration depth using a single load–displacement curve. It was found that the hardness and Young's modulus of GaN/H 2 are lower than those of GaN/N 2. Moreover, pop-in events were revealed for GaN/H 2 , in contrast for GaN/N 2. Fracture was only manifested in the imprint of GaN/N 2 due to its low fracture toughness. Besides, it was disclosed the high sensitivity of loading rate only for GaN/H 2. The GaN/N 2 sample experiences plastic strain relaxation, while GaN/H 2 is a highly stressed sample; hence, it has less dislocation density compared to GaN/N 2 sample. We demonstrated that the used carrier gas influences on GaN epitaxial growth process, which in return deeply affects the resulting dislocation density and dislocation plasticity mechanisms. These latter, tailor the nanomechanical properties of GaN samples and the indentation-induced deformation behavior. [ABSTRACT FROM AUTHOR]