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Structure, mechanical and tribological properties of Mo-S-N solid lubricant coatings

Structure, mechanical and tribological properties of Mo-S-N solid lubricant coatings
Structure, mechanical and tribological properties of Mo-S-N solid lubricant coatings

Solid lubricant coatings deposited by plasma-assisted deposition techniques represent modern way to reduce the coefficient of friction in lubricant-free sliding contacts. Molybdenum disulphide (MoS2 ) is perhaps the most known and applied solid lubricant coating; however, its use is strictly limited by low hardness and environmental sensitivity. To improve mechanical and tribological properties, we doped MoS2 coating with nitrogen. Mo-S-N self-lubricant films were deposited by pulsed d. c. High Target Utilisation Sputtering (HiTUS) in reactive atmosphere. The effect of deposition conditions on chemical composition, structure and mechanical properties of MoSx and Mo-S-N coatings was studied; films with the most promising properties have been selected for tribological testing. MoSx film with the elemental composition sulphur to molybdenum (S/Mo ratio) 1.6 exhibited the coefficients of friction (COFs) in humid air 0.17 and 0.07 for loads 2 and 15 N, respectively. Mo-S-N films were prepared with nitrogen content in a range of 11 to 50 at., whereas S/Mo ratio varied from 1.35 to 0.4. Mo-S-N films were amorphous or nanostructured with nanograins of molybdenum disulphide. Hardness increased with N content up to 14 GPa for film with the highest content of nitrogen. Friction behaviour in humid air was evaluated using a ball-on-disk tribometer. Globally, the doping with N resulted in hardness in Mo–S–N films one order of magnitude higher and wear rate two orders of magnitude lower than in an undoped one, keeping the friction coefficient at the same level or even lower. These coatings showed remarkable friction coefficients in humid air from 0.28 to 0.05 with loads from 2 to 15 N, respectively. The excellent friction properties were attributed to the formation of a thin molybdenum disulphide tribofilm at the sliding interface. HiTUS represents a very promising way of producing thin films on the thermally sensitive substrates (e.g. bearing steel) with desired properties.

Hardness enhancement, Low friction, MoS, Nitrogen, Solid lubricant, Sputtering
0169-4332
1-14
Hudec, Tomáš
498d7571-5532-4e38-bc36-4236e22ad46a
Mikula, Marián
47820357-652d-493a-9a13-10046f75a1f9
Satrapinskyy, Leonid
7fc0c78a-fabd-49a4-823f-b2ac6291c2c6
Roch, Tomáš
0369cab3-ea48-4dae-916c-4e2fb2a01e68
Truchlý, Martin
97f24a75-5387-4807-b854-d3a4c4555cba
Švec, Peter
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Huminiuc, Teodor
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Polcar, Tomáš
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Hudec, Tomáš
498d7571-5532-4e38-bc36-4236e22ad46a
Mikula, Marián
47820357-652d-493a-9a13-10046f75a1f9
Satrapinskyy, Leonid
7fc0c78a-fabd-49a4-823f-b2ac6291c2c6
Roch, Tomáš
0369cab3-ea48-4dae-916c-4e2fb2a01e68
Truchlý, Martin
97f24a75-5387-4807-b854-d3a4c4555cba
Švec, Peter
6b50fcc1-733a-4e4d-8527-9b11aaa70b47
Huminiuc, Teodor
b743b7ba-7541-4f2e-b4be-ea25b088e4c6
Polcar, Tomáš
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2

Hudec, Tomáš, Mikula, Marián, Satrapinskyy, Leonid, Roch, Tomáš, Truchlý, Martin, Švec, Peter, Huminiuc, Teodor and Polcar, Tomáš (2019) Structure, mechanical and tribological properties of Mo-S-N solid lubricant coatings. Applied Surface Science, 486, 1-14. (doi:10.1016/j.apsusc.2019.03.294).

Record type: Article

Abstract

Solid lubricant coatings deposited by plasma-assisted deposition techniques represent modern way to reduce the coefficient of friction in lubricant-free sliding contacts. Molybdenum disulphide (MoS2 ) is perhaps the most known and applied solid lubricant coating; however, its use is strictly limited by low hardness and environmental sensitivity. To improve mechanical and tribological properties, we doped MoS2 coating with nitrogen. Mo-S-N self-lubricant films were deposited by pulsed d. c. High Target Utilisation Sputtering (HiTUS) in reactive atmosphere. The effect of deposition conditions on chemical composition, structure and mechanical properties of MoSx and Mo-S-N coatings was studied; films with the most promising properties have been selected for tribological testing. MoSx film with the elemental composition sulphur to molybdenum (S/Mo ratio) 1.6 exhibited the coefficients of friction (COFs) in humid air 0.17 and 0.07 for loads 2 and 15 N, respectively. Mo-S-N films were prepared with nitrogen content in a range of 11 to 50 at., whereas S/Mo ratio varied from 1.35 to 0.4. Mo-S-N films were amorphous or nanostructured with nanograins of molybdenum disulphide. Hardness increased with N content up to 14 GPa for film with the highest content of nitrogen. Friction behaviour in humid air was evaluated using a ball-on-disk tribometer. Globally, the doping with N resulted in hardness in Mo–S–N films one order of magnitude higher and wear rate two orders of magnitude lower than in an undoped one, keeping the friction coefficient at the same level or even lower. These coatings showed remarkable friction coefficients in humid air from 0.28 to 0.05 with loads from 2 to 15 N, respectively. The excellent friction properties were attributed to the formation of a thin molybdenum disulphide tribofilm at the sliding interface. HiTUS represents a very promising way of producing thin films on the thermally sensitive substrates (e.g. bearing steel) with desired properties.

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More information

Accepted/In Press date: 26 March 2019
e-pub ahead of print date: 25 April 2019
Published date: 30 August 2019
Keywords: Hardness enhancement, Low friction, MoS, Nitrogen, Solid lubricant, Sputtering

Identifiers

Local EPrints ID: 432803
URI: http://eprints.soton.ac.uk/id/eprint/432803
ISSN: 0169-4332
PURE UUID: 942b6c09-e4cf-4017-9cec-1585a87025c8
ORCID for Tomáš Polcar: ORCID iD orcid.org/0000-0002-0863-6287

Catalogue record

Date deposited: 26 Jul 2019 16:30
Last modified: 26 Nov 2021 02:57

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Contributors

Author: Tomáš Hudec
Author: Marián Mikula
Author: Leonid Satrapinskyy
Author: Tomáš Roch
Author: Martin Truchlý
Author: Peter Švec
Author: Teodor Huminiuc
Author: Tomáš Polcar ORCID iD

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