An insight on the MoS2 tribo-film formation to determine the friction performance of Mo-S-N sputtered coatings
An insight on the MoS2 tribo-film formation to determine the friction performance of Mo-S-N sputtered coatings
Amorphous Mo-S-N coatings are known to provide excellent tribological properties in diverse environments due to easy sliding under the influence of MoS2 tribo-films. However, the role of nitrogen incorporation, the formation mechanism of MoS2 tribo-film at the sliding interface and the changes in the friction behaviour under different environments are not fully understood. In this study, an amorphous coating with 30 at. % N was deposited in a semi-industrial reactive direct current magnetron sputtering (DCMS) system, using a single MoS2 target in combination with a secondary plasma source. The coating was predicted to have either a Mo-S-N phase with N filling some of the S sites or a MoS2(N2) structure where the gas molecules prevent the formation of a crystalline lamellar structure. Tribological studies performed in vacuum and ambient air resulted in steady-state COF values of 0.03 and 0.15, respectively. High-resolution transmission electron microscopy (HRTEM) analysis performed on the wear-tracks revealed that the low coefficient of friction (COF) in vacuum was attributed to the formation of a thick and continuous lamellar tribo-film with a low amount of nitrogen. Contrarily, in ambient air, the surface oxidation disturbed the formation of a continuous MoS2 tribo-film from the amorphous coatings, leading to an increase in the COF and wear rate. This study shows through indirect measurements of the chemical composition of the as-deposited coating and wear debris that nitrogen is stored in gaseous form (N2) within the amorphous matrix and is released from the contact during sliding.
Direct current magnetron sputtering, Mo-S-N coatings, Molybdenum disulfide, Nitrogen-alloying mechanism, Solid lubricant coatings, Transition metal dichalcogenides
Hebbar Kannur, Kaushik
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Huminiuc, Teodor
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Yaqub, Talha Bin
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Polcar, Tomas
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Pupier, Christophe
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Héau, Christophe
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Cavaleiro, Albano
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25 February 2021
Hebbar Kannur, Kaushik
1e14583e-f2f6-4769-8a79-fe9679969e4e
Huminiuc, Teodor
b743b7ba-7541-4f2e-b4be-ea25b088e4c6
Yaqub, Talha Bin
e63a18a0-010c-4fef-a40e-67d267ae7fbd
Polcar, Tomas
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Pupier, Christophe
6dca5624-4fff-4e50-86a3-bb7cda1733a3
Héau, Christophe
269805bd-8d38-4d34-93f3-6a8184eb7fc0
Cavaleiro, Albano
83fb0417-34af-4c14-b4b4-b9541e4fc652
Hebbar Kannur, Kaushik, Huminiuc, Teodor, Yaqub, Talha Bin, Polcar, Tomas, Pupier, Christophe, Héau, Christophe and Cavaleiro, Albano
(2021)
An insight on the MoS2 tribo-film formation to determine the friction performance of Mo-S-N sputtered coatings.
Surface and Coatings Technology, 408, [126791].
(doi:10.1016/j.surfcoat.2020.126791).
Abstract
Amorphous Mo-S-N coatings are known to provide excellent tribological properties in diverse environments due to easy sliding under the influence of MoS2 tribo-films. However, the role of nitrogen incorporation, the formation mechanism of MoS2 tribo-film at the sliding interface and the changes in the friction behaviour under different environments are not fully understood. In this study, an amorphous coating with 30 at. % N was deposited in a semi-industrial reactive direct current magnetron sputtering (DCMS) system, using a single MoS2 target in combination with a secondary plasma source. The coating was predicted to have either a Mo-S-N phase with N filling some of the S sites or a MoS2(N2) structure where the gas molecules prevent the formation of a crystalline lamellar structure. Tribological studies performed in vacuum and ambient air resulted in steady-state COF values of 0.03 and 0.15, respectively. High-resolution transmission electron microscopy (HRTEM) analysis performed on the wear-tracks revealed that the low coefficient of friction (COF) in vacuum was attributed to the formation of a thick and continuous lamellar tribo-film with a low amount of nitrogen. Contrarily, in ambient air, the surface oxidation disturbed the formation of a continuous MoS2 tribo-film from the amorphous coatings, leading to an increase in the COF and wear rate. This study shows through indirect measurements of the chemical composition of the as-deposited coating and wear debris that nitrogen is stored in gaseous form (N2) within the amorphous matrix and is released from the contact during sliding.
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More information
Accepted/In Press date: 20 December 2020
e-pub ahead of print date: 2 January 2021
Published date: 25 February 2021
Additional Information:
Funding Information:
This project has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement No. 721642: SOLUTION. The electron microscopy imaging was performed with the support of CEITEC Nano Research Infrastructure (ID LM2015041, MEYS CR, 2016?2019), CEITEC Brno University of Technology. The authors would also like to thank funding from CEMMPRE ? UID/EMS/00285/2019 [co-financed via FEDER and FCT (COMPETE)].
Funding Information:
This project has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement No. 721642 : SOLUTION. The electron microscopy imaging was performed with the support of CEITEC Nano Research Infrastructure (ID LM2015041, MEYS CR, 2016–2019), CEITEC Brno University of Technology. The authors would also like to thank funding from CEMMPRE – UID/EMS/00285/2019 [co-financed via FEDER and FCT (COMPETE)].
Publisher Copyright:
© 2020 Elsevier B.V.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Keywords:
Direct current magnetron sputtering, Mo-S-N coatings, Molybdenum disulfide, Nitrogen-alloying mechanism, Solid lubricant coatings, Transition metal dichalcogenides
Identifiers
Local EPrints ID: 454828
URI: http://eprints.soton.ac.uk/id/eprint/454828
ISSN: 0257-8972
PURE UUID: 2783c35d-f759-45b5-ab1a-c1118dd12513
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Date deposited: 24 Feb 2022 21:52
Last modified: 18 Mar 2024 03:19
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Contributors
Author:
Kaushik Hebbar Kannur
Author:
Teodor Huminiuc
Author:
Talha Bin Yaqub
Author:
Christophe Pupier
Author:
Christophe Héau
Author:
Albano Cavaleiro
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