Tribological Behaviors of Graphene Sheets as Water-Based Lubricant Additives: Synthesis, Characterization and Long-Term Storage

Abstract

As a sustainable and environmentally-friendly lubricant base, water holds significant promise in the tribology field. However, its inherent tribological properties are often found to be insufficient for industrial requirements. To overcome this limitation, micron-sized graphene sheets have been introduced as additives to enhance the lubricating capabilities of water. Various concentrations of graphene-dispersed aqueous solutions were prepared, and the tribological characteristics of the graphene-enhanced water-based lubricants and the static storage for 6 months were systematically analyzed. The results indicated that the friction coefficient and wear volume of the tribo-pair were significantly reduced through the incorporation of graphene sheets, thereby improving durability, and have long-term storage stability. Notably, under the experimental conditions, a 0.2% mass concentration of graphene in the aqueous lubricant exhibited exceptional tribological performance and long-term storage stability effect, achieving an 80% reduction in friction coefficient and a 78% decrease in wear volume with 14000 cycles friction test. Wear morphology analysis indicated that after adding graphene sheets to the aqueous solution, micro-plastic deformation occurs on the worn surface of the steel plate, and the primary wear mechanism of the 316L stainless steel plate shifted from abrasive wear to fatigue wear. The wear profile of the GCr15 counter ball changes from a circular profile to a rectangular-like profile. The main reason is that the graphene sheets in the aqueous solution can enter the contact interface during the friction process, hindering direct contact between the friction pair.

Keywords: Tribological behaviors, Graphene, water-based lubricant, Wear morphology analysis, long-term storage