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Calcium sulfonate complex greases (CSCG) have proven to be a sustainable alternative to lithium complex greases, which still require appropriate additives to deliver lubrication performance benefits under extreme working conditions such as heavy load, high speed, and high temperature. The anti-wear and friction reducing properties of CSCG enhanced by two-dimensional MoS2 nanosheets (2D MoS2) with a narrow lateral size and thickness distributions were evaluated by a four-ball tribometer. The results showed that the CSCG with 0.6 wt.% 2D MoS2 performs best, with a 56.4% decrease in average friction coefficient (AFC), 16.5% reduction in wear scar diameter (WSD), 14.3% decrease in surface roughness, and a 59.4% reduction in average wear depth. Combining SEM-EDS images, Raman, and X-ray photoelectron spectra, it is illustrated that the physical transferred film and tribo-chemical film consisting of MoS2, Fe2O3, FeSO4, CaCO3, CaO, and MoO3 were generated on the worn surface, which improves the lubrication performance of CSCG considerably. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) have been considered as novel and economic alternatives to traditional lubricants because of their similar physicochemical performance. In this study, choline chloride (ChCl) DESs were successfully synthesized via hydrogen-bonding networks of urea and thiourea as the hydrogen bond donors (HBDs). The as-synthesized ChCl-urea and ChCl-thiourea DESs had excellent thermal stability and displayed good lubrication between steel/steel tribo-pairs. The friction coefficient and wear rate of ChCl-thiourea DES were 50.1% and 80.6%, respectively, lower than those of ChCl-urea DES for GCr15/45 steel tribo-pairs. However, for GCr15/Q45 steel, ChCl-urea DES decreased the wear rate by 85.0% in comparison to ChCl-thiourea DES. Under ChCl-thiourea DES lubrication, the tribo-chemical reaction film composed of FeS formed at the interfaces and contributed to low friction and wear. However, under high von Mises stress, the film could not be stably retained and serious wear was obtained through direct contact of friction pairs. This illustrated that the evolution of the tribo-chemical reaction film was responsible for the anti-friction and anti-wear properties of the DESs. [ABSTRACT FROM AUTHOR]

Calcium sulfonate complex greases (CSCG) have proven to be a sustainable alternative to lithium complex greases, which still require appropriate additives to deliver lubrication performance benefits under extreme working conditions such as heavy load, high speed, and high temperature. The anti-wear and friction reducing properties of CSCG enhanced by two-dimensional MoS2 nanosheets (2D MoS2) with a narrow lateral size and thickness distributions were evaluated by a four-ball tribometer. The results showed that the CSCG with 0.6 wt.% 2D MoS2 performs best, with a 56.4% decrease in average friction coefficient (AFC), 16.5% reduction in wear scar diameter (WSD), 14.3% decrease in surface roughness, and a 59.4% reduction in average wear depth. Combining SEM-EDS images, Raman, and X-ray photoelectron spectra, it is illustrated that the physical transferred film and tribo-chemical film consisting of MoS2, Fe2O3, FeSO4, CaCO3, CaO, and MoO3 were generated on the worn surface, which improves the lubrication performance of CSCG considerably.

The tribological behaviours of Si 3 N 4 -hBN (the content of the hBN is 0%, 5%,10%,20% and 30%) composites sliding on metal under dry friction condition at different sliding speeds were investigated by using an MMW-1 type vertical universal friction and wear tester. Research shows that the friction coefficients of the sliding pairs represent a downward trend with the increase of the sliding speed. And the addition of hBN could effectively improve the tribological performance of the Si 3 N 4 -hBN/ASS tribocouple. Especially, for the SN10 (Si 3 N 4 -10%hBN)/ASS pair, the friction coefficient decreased from 0.69 at a sliding speed of 0.52 m/s to 0.51 at a sliding speed of 0.86 m/s, and continuously decreased to 0.12 at a speed of 1.73 m/s. However, the negative wear which closed to zero appeared on the SN10 pin mated with the ASS disc at a speed of 1.73 m/s. During the friction process, higher sliding speed provided a favourable condition for the chemical reaction between the worn surface of the friction pairs and the air. Meanwhile the surface analysis indicated that a surface film consisting of Fe 2 O 3 , SiO 2 and B 2 O 3 was formed on the worn surface of the SN10/ASS tribocouple also at a speed of 1.73 m/s. The surface film lubricated the worn surfaces and protected both of pin and disc from being further wore. Compared with Si 3 N 4 -hBN/ASS pairs, the tribological properties of Si 3 N 4 -hBN/45# pairs were poor under the same experimental conditions. [ABSTRACT FROM AUTHOR]