Ultra-low wear technology provides an effective solution to prolong the service life of mechanical equipment. However, there are still significant challenges in achieving ultra-low wear at the steel/steel interface over long periods. In this work, a PAO10-SPAN65 composite semisolid lubricant (PAO10/SP65) was designed with sorbitan tristearate (SPAN65) and base oil poly α-olefin 10 (PAO10). The wear rate of the steel lubricated with PAO10/SP65 (1.31×10⁻⁸ mm³·N⁻¹·m⁻¹) was 96% lower than that of PAO10 (3.52×10⁻⁷ mm³·N⁻¹·m⁻¹). In addition, after 10 h of friction testing at a contact pressure of 0.82 GPa, the wear of the steel surface is still close to zero, with a wear rate of 4.13×10⁻⁹ mm³·N⁻¹·m⁻¹. This study provides a new design idea for realizing ultra-low wear of engineering steel.

Adequate lubrication of the steel/steel interface is an effective way to reduce wear and prolong the service life of mechanical equipment. However, achieving the green ultra-low wear between steel and steel remains a challenge. In this work, a semi-solid deionized water (DIW)/sorbitan monostearate (Span 60) composite lubricant (DSP) is designed to achieve ultra-low wear at the steel/steel interface. Compared with DIW lubrication, the friction coefficient of DSP was reduced by 75%, and the wear rate was reduced by 2 orders of magnitude. At a contact pressure of 791.5 MPa, the wear rate also increases with increasing number of cycles 10,000 (5.82×10⁻⁸ mm³·N⁻¹·m⁻¹) and 20,000 (7.62×10⁻⁸ mm³·N⁻¹·m⁻¹), but ultra-low wear can still be achieved. The ultra-low wear was attributed to sufficient adsorption and the hydrogen-bond network of the lubricant at the friction pair surface, which effectively reduced the direct contact of the friction pair. This work inspires research on green ultra-low wear lubricants and promotes the broad application of ultra-low wear technology in engineering.

Electrostatic accumulation at the oil-lubricated interface may cause electrostatic adsorption of impurities and oil aging. However, there are still great challenges in terms of the triboelectric mechanism and electrostatic regulation under the oil lubrication state. Under poly-α-olefin 4 (PAO 4) lubrication, the electrostatic accumulation at the interface is serious (−1,873 V), which can be attributed to the inhibitory effect of lubricating oil on the transfer film and electrostatic breakdown in interfacial air. When sorbitan monostearate (Span 60) was added to PAO oil, the surface potential of polytetrafluoroethylene (PTFE) was significantly reduced because the adsorption of Span 60 inhibited electron transfer at the interface. This study reveals the triboelectric mechanism under oil lubrication from a tribological perspective and offers new strategies for electrostatic protection of oil-lubricating interfaces.