Research on ultra-low wear of steel/steel based on water/Span 60 composite semi-solid lubricant

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.