On the S/W stoichiometry and triboperformance of WSxC(H) coatings deposited by magnetron sputtering

Cao, Huatang; Wen, Feng; Kumar, Sumit; Rudolf, Petra; Hosson, J.T.M. de; Pei, Yu

doi:10.1016/j.surfcoat.2018.04.040

Cited by 23 publications

(18 citation statements)

References 52 publications

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“…Differences are probably due to the slightly inferior morphological appearance as well as the small compositional differences. Overall, the coatings revealed comparable wear resistance to those available for TMD-C films in the literature [14,15,34,35] A small reduction in the CoF was verified for the MoSe and low carbon content coatings (MoSeC24 and MoSeC33). However, for the films with increased carbon content, the friction reduction was even higher.…”

Section: Tribological Propertiessupporting

confidence: 61%

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On the Microstructural, Mechanical and Tribological Properties of Mo-Se-C Coatings and Their Potential for Friction Reduction against Rubber

et al. 2021

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Friction and wear contribute to high energetic losses that reduce the efficiency of mechanical systems. However, carbon alloyed transition metal dichalcogenide (TMD-C) coatings possess low friction coefficients in diverse environments and can self-adapt to various sliding conditions. Hence, in this investigation, a semi-industrial magnetron sputtering device, operated in direct current mode (DC), is utilized to deposit several molybdenum-selenium-carbon (Mo-Se-C) coatings with a carbon content up to 60 atomic % (at. %). Then, the carbon content influence on the final properties of the films is analysed using several structural, mechanical and tribological characterization techniques. With an increasing carbon content in the Mo-Se-C films, lower Se/Mo ratio, porosity and roughness appeared, while the hardness and compactness increased. Pin-on-disk (POD) experiments performed in humid air disclosed that the Mo-Se-C vs. nitrile butadiene rubber (NBR) friction is higher than Mo-Se-C vs. steel friction, and the coefficient of friction (CoF) is higher at 25 °C than at 200 °C, for both steel and NBR countersurfaces. In terms of wear, the Mo-Se-C coatings with 51 at. % C showed the lowest specific wear rates of all carbon content films when sliding against steel. The study shows the potential of TMD-based coatings for friction and wear reduction sliding against rubber.

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Section: Tribological Propertiessupporting

confidence: 61%

Section: Resultsmentioning

confidence: 62%

On the Microstructural, Mechanical and Tribological Properties of Mo-Se-C Coatings and Their Potential for Friction Reduction against Rubber

et al. 2021

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“…On the other hand, amorphous carbon coatings provide high hardness but are not suitable for applications that work in dry atmospheres. Therefore, a combination of carbon and TMDs was explored by various authors [18,[29][30][31][32][33][34][35][36], with the main idea to harvest the best properties of both materials and prepare the ultimate solid lubricant that will be able to reduce friction in diverse environments.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of DC and RF Sputtered MoSe2 Coatings Containing Carbon—An Approach to Optimize Stoichiometry, Microstructure, Crystallinity and Hardness

et al. 2020

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Low stoichiometry, low crystallinity, low hardness and incongruencies involving the reported microstructure have limited the applicability of TMD-C (Transition metal dichalcogenides with carbon) solid-lubricant coatings. In this work, optimized Mo–Se–C coatings were deposited using confocal plasma magnetron sputtering to overcome the above-mentioned issues. Two different approaches were used; MoSe2 target powered by DC (direct current) or RF (radio frequency) magnetron sputtering. Carbon was always added by DC magnetron sputtering. Wavelength dispersive spectroscopy displayed Se/Mo stoichiometry of ~2, values higher than the literature. The Se/Mo ratio for RF-deposited coatings was lower than for their DC counterparts. Scanning electron microscopy showed that irrespective of the low carbon additions, the Mo–Se–C coatings were highly compact with no vestiges of columnar growth due to optimal bombardment of sputtered species. Application of substrate bias further improved compactness at the expense of lower Se/Mo ratio. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy confirmed the presence of MoSe2 crystals, and (002) basal planes. Even very low carbon additions led to an improvement of the hardness of the coatings. The work reports a comparison between RF and DC sputtering of MoSe2 coatings with carbon and provides a guideline to optimize the composition, morphology, structure, and mechanical properties.

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“…The films deposited by these different routes were studied in a time span of several years, and it is still not clear which is the best route for potential upscaling. A recent study performed on W-S-C(H) coatings [13] has shown that co-sputtered hydrogen-free coatings display the best tribological performance, with evidence that the C phase plays a role in the frictional response during sliding in ambient air conditions, contrary to the studies done by Polcar and Cavaleiro. A major issue regarding the synthesis of TMD-containing thin films by way of magnetron sputtering is the sub-stoichiometry in relation to the S/M ratio (M-transition metal, S-chalcogen atom), which is often much lower than the stoichiometric value of 2. The sub-stoichiometry has a strong effect on the tribological properties and the hardness of the films.…”

Section: Introductionmentioning

confidence: 77%

Synthesis, Microstructural, and Mechano-Tribological Properties of Self-Lubricating W-S-C(H) Thin Films Deposited by Different RF Magnetron Sputtering Procedures

et al. 2020

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Carbon-alloyed transition metal dichalcogenide (TMD) coatings have great potential for providing a good tribological response in diverse operating environments. There are different ways to synthesize these coatings by magnetron sputtering, with no clear indication of the best possible route for potential upscaling. In this study, tungsten-sulfur-carbon (W-S-C) coatings were deposited by radio frequency (RF) magnetron sputtering via four different methods. All coatings were sub-stoichiometric in terms of the S/W ratio, with the bombardment of the growing film with backscattered Ar neutrals being the main mechanism governing the S/W ratio. The crystallinity of the films was dependent on the C and S contents. X-ray photoelectron spectroscopy (XPS) revealed W-S and W-C bonding in all coatings. Raman spectroscopy showed the presence of an a-C phase with predominant sp2 bonding. The hardness of the coatings may be related to the C content and the S/W ratio. A friction coefficient of 0.06–0.08 was achieved during sliding in ambient air by the coatings deposited in non-reactive mode with optimal C contents. The results indicate that sputtering in non-reactive mode should be the method of choice for synthesis of these coatings.

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On the S/W stoichiometry and triboperformance of WSxC(H) coatings deposited by magnetron sputtering

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Cited by 23 publications

References 52 publications

On the Microstructural, Mechanical and Tribological Properties of Mo-Se-C Coatings and Their Potential for Friction Reduction against Rubber

On the Microstructural, Mechanical and Tribological Properties of Mo-Se-C Coatings and Their Potential for Friction Reduction against Rubber

Comparative Study of DC and RF Sputtered MoSe2 Coatings Containing Carbon—An Approach to Optimize Stoichiometry, Microstructure, Crystallinity and Hardness

Synthesis, Microstructural, and Mechano-Tribological Properties of Self-Lubricating W-S-C(H) Thin Films Deposited by Different RF Magnetron Sputtering Procedures

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