Influence of Ti addition on the structure and properties of low-friction W–S–C coatings

Sundberg, Jill; Nyberg, Harald; Särhammar, Erik; Gustavsson, Fredrik; Kubart, Tomáš; Nyberg, Tomas; Jacobson, Staffan; Jansson, Ulf

doi:10.1016/j.surfcoat.2013.05.032

Cited by 45 publications

(30 citation statements)

References 58 publications

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“…For all samples containing N, only a broad bump is observed, implying that the films are X-ray amorphous. The phenomenon of decreasing crystallinity with increasing addition of another element has previously been observed for WS 2 , and the related MoS 2 , on addition of a wide range of elements, such as N [10], C [9][10][11], Ti [1,2], Cr [4,38] and Au [6,7]. Furthermore, the lack of substrate heating decreases the possibilities of the atoms arranging themselves on arrival at the substrate, meaning that the pure W-S film is also of relatively poor crystallinity.…”

Section: Resultsmentioning

confidence: 72%

“…To make full use of the possibility of WS 2 superlubricity, one would require a stable surface with good load-bearing capacity and wear resistance, on which a tribofilm of aligned WS 2 crystallites is formed. To obtain this, WS 2 and MoS 2 have been combined with metals, for example Ti [1,2], Cr [3,4], Ni [5], Au [6,7] and Pb [8], as well as non-metals, such as C [9][10][11] and N [10]. The film itself then contains embedded nanocrystalline TMD grains, and in some cases no distinguishable TMD phase at all.…”

Section: Introductionmentioning

confidence: 99%

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Amorphous W–S–N thin films: The atomic structure behind ultra-low friction

et al. 2015

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Amorphous W-S-N in the form of thin films has been identified experimentally as an ultra-low friction material, enabling easy sliding by the formation of a WS 2 tribofilm. However, the atomic-level structure and bonding arrangements in amorphous W-S-N, which give such optimum conditions for WS 2 formation and ultra-low friction, are not known. In this study, amorphous thin films with up to 37 at.% N are deposited, and experimental as well as state-of-the-art ab initio techniques are employed to reveal the complex structure of W-S-N at the atomic level. Excellent agreement between experimental and calculated coordination numbers and bond distances is demonstrated. Furthermore, the simulated structures are found to contain N bonded in molecular form, i.e. N 2 , which is experimentally confirmed by near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy analysis. Such N 2 units are located in cages in the material, where they are coordinated mainly by S atoms. Thus this ultra-low friction material is shown to be a complex amorphous network of W, S and N atoms, with easy access to W and S for continuous formation of WS 2 in the contact region, and with the possibility of swift removal of excess nitrogen present as N 2 molecules.

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Section: Resultsmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Amorphous W–S–N thin films: The atomic structure behind ultra-low friction

et al. 2015

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“…[22][23][24][25][26][27][28] Besides, the works using nanoscratch method are also executed in other fields. 29,30 In addition, due to the fine output performance of the displacement, the piezoelectric actuator is usually utilized to realize the precise feed motion. 31,32 In this article, the piezoceramic is adopted according to the preceding works.…”

Section: Introductionmentioning

confidence: 99%

A novel nanoscratch device compatible with commercial microscope for in situ tests of materials’ mechanics

Zhao

Zhang

et al. 2016

Advances in Mechanical Engineering

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For exploring the mechanical properties and behaviors of new materials, a novel in situ nanoscratch device compatible with commercial microscope has been developed. The developed device with specific dimensions of 178 mm 3 165 mm 3 78 mm includes the coarse positioning module, the precise feed module, the measurement module, and the control module. Integrating the servo motor, worm and gears, ball screw, flexure hinge, and piezoelectric actuator, the device can realize macroscopical coarse positioning motion and precise feed motion. A novel arrangement of load sensor and indenter with no middle chain is used to reduce the measurement error. Closed-loop control system is established to guarantee the accuracy of load and displacement control. Mechanical properties of the developed device have been proved by calibrating the load sensor, finite element analysis of flexure hinge, and verifying the output performance. The in situ nanoscratch test has been conducted on the single crystal copper. The captured images and finite element analysis prove the feasibility and accuracy of the developed device.

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“…If the added element forms a hard phase, on its own or together with an already existing element, even further hardness increases can be achieved. This has also been the goal (and result) in studies where several elements, such as Cr-N and Ti-C, have been added to the W-S system, resulting in the formation of hard phases of CrN and TiC, respectively [6,7].…”

Section: Introductionmentioning

confidence: 99%

“…On the contrary, even completely amorphous coatings have been shown to form crystalline WS 2 tribofilms when exposed to sliding contact [6,8]. These tribofilms form on the surface of the coatings, and also as a transfer film on the counter surface, and it is within these that sliding occurs.…”

Section: Introductionmentioning

confidence: 99%

Influence of composition, structure and testing atmosphere on the tribological performance of W–S–N coatings

Sundberg

Nyberg

Särhammar

et al. 2014

Surface and Coatings Technology

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W-S-N coatings deposited by reactive magnetron sputtering offer the possibility of ultra-low friction in unlubricated sliding. In this work, W-S-N coatings of different composition and structure have been deposited, characterised and evaluated with respect to the tribological performance and tribofilm formation. The composition was varied by changing the flow of N 2 into the deposition chamber, leading to N contents ranging from 0 to 47 at.%. W-S-N coatings deposited without substrate heating are amorphous, while substrate heating results in coatings containing nanocrystalline tungsten sulphide (WS x ) for low N contents, and nanocrystalline tungsten nitride (W y N) at a high N content. The coatings were tribologically tested against steel balls in four different atmospheres-dry N 2 , dry air, humid N 2 and humid air-to study the effects of atmospheric O 2 and H 2 O both separately and simultaneously. In dry N 2 , all coatings exhibited an excellent performance with very low friction (μ ≈ 0.02) and wear. Notably, this included the N-richest and hardest coating, containing nanocrystalline W y N and only 13 at.% of S. The friction and wear increased on changing the atmosphere, in the order of dry airhumid N 2 -humid air. In these three non-inert atmospheres, the friction and wear also increased with increasing N content of the coating. It is thus concluded that the presence of O 2 , the presence of H 2 O, and a high N content (i.e., low W and S contents) are three factors increasing the risk of high friction and wear, especially when occurring together. Raman spectroscopy mapping of the contact surfaces on the coatings and the balls showed that low friction and wear is connected to the presence of WS 2 tribofilms in the contact, and that the three previously mentioned factors affect the formation and function of this tribofilm.

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Influence of Ti addition on the structure and properties of low-friction W–S–C coatings

Cited by 45 publications

References 58 publications

Amorphous W–S–N thin films: The atomic structure behind ultra-low friction

Amorphous W–S–N thin films: The atomic structure behind ultra-low friction

A novel nanoscratch device compatible with commercial microscope for in situ tests of materials’ mechanics

Influence of composition, structure and testing atmosphere on the tribological performance of W–S–N coatings

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