316 steel is a widely used material for mechanical components, and more investigations have been reported due to its mechanical properties and corrosion resistance, while its tribological properties have not received enough attention. Friction and wear is the result of material transfer at the contact surface caused by mutual motion between two objects in touch. As we known, friction and wear not only wastes resources, but also seriously shortens the lifespan of mechanical parts. Lubrication is the most effective way to reduce friction and wear, which can minimize the contact area between the interfaces resulting in reducing the wear and friction. Besides, liquid lubrication is widely used in mechanical, automotive, aviation, and other industrial industries because of its low coefficient of friction, low noise, and light wear. Therefore, investigation on 316 steel's tribological behavior under liquid lubrication is necessary. The lubricating properties of polyalphaolefins are exceptionally outstanding, however, their limited biodegradability poses a potential threat to environmental safety, thus necessitating the exploration of more environmentally sustainable lubricants is imperative.

Based on the polyol esters with the characteristics of low toxicity, biodegradability, and good lubrication performance, the lubricating performance of polyalphaolefin (PAO4) and pentaerythritol tetraoleate (PETO) between the interfaces of 316 stainless steel at 2 N, 10 N, and 500 r/min were investigated in this work. The tribological results showed that compared to the dry frictional condition at 2 N and 500 r/min, the wear volumes of the PETO and PAO4 systems decreased by 2 and 1.7 times, respectively. As compared with the dry friction condition under 10 N and 500 r/min, the wear volumes of the PETO and PAO4 systems decreased by 12 and 8.9 times, respectively, and the wear resistance of PETO system was superior to that of the PAO4 system. Raman spectroscopy and TEM results showed that PETO and PAO4 was transformed into the graphene-like layered structure through the friction-induced effect, which effectively improved the friction-reduction and anti-wear performance.