TY - JOUR
T1 - An insight on the MoS2 tribo-film formation to determine the friction performance of Mo-S-N sputtered coatings
AU - Hebbar Kannur, Kaushik
AU - Huminiuc, Teodor
AU - Yaqub, Talha Bin
AU - Polcar, Tomas
AU - Pupier, Christophe
AU - Héau, Christophe
AU - Cavaleiro, Albano
N1 - 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.
PY - 2021/2/25
Y1 - 2021/2/25
N2 - 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.
AB - 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.
KW - Direct current magnetron sputtering
KW - Mo-S-N coatings
KW - Molybdenum disulfide
KW - Nitrogen-alloying mechanism
KW - Solid lubricant coatings
KW - Transition metal dichalcogenides
UR - http://www.scopus.com/inward/record.url?scp=85099210489&partnerID=8YFLogxK
UR - https://eprints.soton.ac.uk/454828/
U2 - 10.1016/j.surfcoat.2020.126791
DO - 10.1016/j.surfcoat.2020.126791
M3 - Article
AN - SCOPUS:85099210489
SN - 0257-8972
VL - 408
JO - Surface and Coatings Technology
JF - Surface and Coatings Technology
M1 - 126791
ER -