Superior Lubrication Performance Achieved by a Water-Based Lubricant with Auricularia auricula Polysaccharide as a Green Additive

Green lubricating materials have attracted widespread attention because they comply with environmental regulations. In this study, the tribological performance of Auricularia auricula polysaccharide (AAP) as a water-based lubricant additive was systematically investigated under different frictional conditions and lubricant concentrations using a Si3N4/17–4PH stainless-steel friction pair. The lubrication mechanism of AAP was elucidated through an analysis of the chemical composition of the worn surfaces. The results indicate that, compared with deionized water lubrication, the 5.0 wt % AAP lubricant reduces the average coefficient of friction (COF) and wear rate of the friction pair by 71% and 84%, respectively. In addition, at a concentration of 2.0 wt %, the AAP lubricant can maintain a stable low-friction state during long-term friction tests lasting up to 6 h with an average COF of approximately 0.09. The superior lubrication performance of the AAP lubricant results from the synergistic effects of an adsorbed layer, a hydration layer, and an inorganic friction film, as confirmed by XPS and SEM measurements coupled with EDS analyses. These findings provide important guidance for the development of low-cost, environmentally friendly, renewable, and biodegradable water-based lubricant additives.