Titanium doped MoSe₂ coatings – Synthesis, structure, mechanical and tribological properties investigation

Hudec, Tomáš, Bondarev, Andrey, Izai, Vitalii, Šroba, Viktor, Satrapinskyy, Leonid, Roch, Tomáš, Turiničová, Veronika, Grančič, Branislav, Polcar, Tomáš and Mikula, Marián (2021) Titanium doped MoSe₂ coatings – Synthesis, structure, mechanical and tribological properties investigation. Applied Surface Science, 568, [150990]. (doi:10.1016/j.apsusc.2021.150990).

Abstract

In this work, we doped sputtered MoSe₂ coatings with Ti to improve their mechanical and tribological properties. Mo-Se-Ti coatings were prepared onto steel discs by High Target Utilisation Sputtering (HiTUS). The Ti was in the range 7–31 at.%, which led to Se/Mo ratios of 1.7–2.7. The Mo-Se-Ti coatings possessed a polycrystalline structure for the lower Ti contents and became amorphous when Ti content was above approx. 18 at.%. The hardness of the initially soft (0.3 GPa) pure MoSe₂ coatings was dramatically improved with Ti additions (up to 7.5 GPa). Sliding experiments confirmed excellent tribological properties: coefficient of friction values from 0.02 to 0.08 and very low wear rates (8×10^-8mm³N^-1m⁻¹) of the Ti-containing coatings tested in the humid air at the loads in the range of 2–45 N. The outstanding self-lubricant properties of Mo-Se-Ti coatings were attributed to the transformation of the topmost amorphous part of the coating into crystalline MoSe₂ tribofilm while preserving inner parts of the coating in as-deposited state ensuring good load-bearing capacity. There is strong experimental evidence that Ti has a gettering effect in the tribological contact, which protects MoSe₂ tribofilm against oxidation.

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Contributors

Author: Tomáš Polcar

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