Abstract
WS2-C is produced from a hydrothermal reaction, in which WS2 nano-sheets are coated with carbon, using glucose as the carbon source. In order to investigate the tribological properties of WS2-C as a lubricant additive, WS2-C was modified by surfactant Span80, and friction tests were carried out on an MRS-10A four-ball friction and wear tester. The results show that Span80 can promote the dispersibility of WS2-C effectively in base oil. Adding an appropriate concentration of WS2-C can improve the anti-wear and anti-friction performance of the base oil. The friction coefficient reached its lowest point upon adding 0.1 wt % WS2-C, reduced by 16.7% compared to the base oil. Meanwhile, the wear scar diameter reached its minimum with 0.15 wt % WS2, decreasing by 26.45%. Moreover, at this concentration, the depth and width of the groove and the surface roughness on the wear scar achieved their minimum. It is concluded that WS2-C dispersed in oil could enter friction pairs to avoid their direct contact, thereby effectively reducing friction and wear. At the same time, WS2-C reacts with the friction matrix material to form a protective film, composed of C, Fe2O3, FeSO4, WO3, and WS2, repairing the worn surface.
Highlights
For a long time, lubricating oil was the first choice to solve the problem of friction and wear due to its high effectiveness
Sade et al [8] demonstrated that nano-WS2 modified by Span80 could noticeably reduce the friction coefficient, as well as the depth and width of wear scars, using a ball-on-disc test
Nano-sheets with carbon coating is shown in Figure 3b, in which the width of the nano-sheets increased sharply. This planar growth of WS2 nano-sheets was related to the high temperature and high pressure in the hydrothermal reaction, while the low growth in thickness was due to the carbon coating
Summary
For a long time, lubricating oil was the first choice to solve the problem of friction and wear due to its high effectiveness. The advent of nano-additives in lubricant [1,2,3], allowing a better performance in terms of tribological characteristics, greatly improves the lubricity of traditional lubricants. Due to their great lubricity, carbon material [4,5,6,7] and flake nano-WS2 are used as nano-additives in lubrication. Wu et al [9] compared the friction properties of micro- and nano-flake WS2 as lubricant additives Their results showed that the lubricating performance of WS2 with a diameter of 90 nm was slightly better than that of WS2 with a diameter of 2 μm, but the difference in friction coefficient was only about 5%. This means that WS2 with a diameter of microns has good lubricating performance
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