This research thoroughly examined the tribological characteristics of polyalphaolefin (PAO4) oil, both with and without the incorporation of methyl silicone resin. The evaluation of anti-wear properties and friction reduction was conducted using a four-ball tester for friction and wear. The incorporation of methyl silicone resin into PAO4 at 25 °C significantly reduced the wear scar diameter (WSD), achieving minimum values at a concentration of 0.02 wt.%. PAO4 with 0.02 wt.% methyl silicone resin shows excellent wear resistance at different temperatures. A detailed analysis of the wear scar surfaces and wear debris was conducted using scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, 3D surface profiler and TEM. The results compellingly demonstrate that the remarkable improvement in wear resistance is predominantly due to the strategic formation of SiO₂ nanoparticles during the friction process. These SiO₂ particles not only adeptly fill the surface gaps at the friction interface but also crucially contribute to the formation of a robust tribochemical film, which is instrumental in enhancing wear performance.

In this study, we successfully synthesized two types of nitrogen–phosphorus co-doped carbon dots (CDs), namely 6NP-CDs and eNP-CDs, and incorporated them as additives into ethylene glycol-based lubricants. We systematically evaluated the effects of these CD additives on the tribological properties of the lubricants through four-ball friction experiments. The experimental results demonstrate that lubricants enhanced with the CDs exhibit significantly improved tribological properties compared to the base lubricant, particularly in terms of anti-wear performance. Notably, 6NP-CDs exhibited superior wear resistance and friction reduction at concentrations of 0.1 wt.% and 0.2 wt.%. Furthermore, increasing the concentration of eNP-CDs further reduced the friction coefficient of the base lubricant, and at its optimal concentration, it outperformed 6NP-CDs in terms of wear resistance and friction reduction. Molecular structure analysis indicates that the concentration of nitrogen and phosphorus atoms, as well as the chain length of functional groups, significantly influence friction characteristics. Specifically, a greater content of heteroatoms and longer chain lengths correlate with improved friction performance. The results suggest that incorporating 6NP-CDs and eNP-CDs into ethylene glycol-based lubricants can lead to significant enhancements in tribological performance under heavy loads.

This study investigates spherical methyl silicone resin, a potentially environmentally friendly additive free of sulfur, phosphorus, and chlorine, as a lubricant additive in polyethylene glycol 200 (PEG 200) base oils. We evaluated concentration-response characteristics and tribological performance across PEG base oils containing 0.01–0.05 wt% resin. Tribological testing was conducted with a four-ball wear tester at 98 N and 1450 rpm for 30 min. All tested concentrations demonstrated excellent friction-reduction and anti-wear performance, with an optimal efficacy observed at 0.02 wt%. Surface characterization was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. This friction-reducing and anti-wear performance is attributed to the formation of silicon-oxygen species and graphene-like carbon structures, thereby effectively suppressing direct surface contact and mitigating wear. Consequently, spherical methyl silicone resin demonstrates considerable potential as a green lubricant additive for bearing steel applications.