Purpose The purpose of this paper is to investigate the rheological and tribological properties of nano-silica-based grease (SGs) prepared from different silicone oils under high-temperature conditions, thereby providing the foundation for solving high-temperature lubrication problems of mechanical components. Design/methodology/approach In this study, four SGs were prepared using different silicone oils with good high-temperature performance, combined with nano-fumed silica. The influence of the silicone oils on the thermal stability, high-temperature rheological properties and tribological performance of the SGs were investigated using a thermogravimetric analyzer (TGA), a rotational rheometer and a linear oscillation test machine (SRV). To elucidate the lubrication mechanisms, surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Findings Thermogravimetric analysis indicated that all four SGs exhibited good thermal stability, with SG-vinyl silicone oil demonstrating the highest. SG-Polydimethylsiloxane (PDMS) showed the highest structural strength at elevated temperatures. Tribological test results revealed that SG-Hydroxyl-terminated polydimethylsiloxane (OH-PDMS) exhibited the best friction-reducing performance, while SG-PDMS exhibited the best antiwear performance. In contrast, SG-Phenylmethyl silicone oil exhibited the poorest performance in both friction reduction and antiwear properties, primarily due to differences in oil wettability. Originality/value Analysis of the lubrication mechanism reveals that the lubricating effect of the SGs primarily stems from the synergistic action of a carbon-based lubricating film and a nano-silica deposition film formed on friction pair surfaces. This mechanism provides a more comprehensive understanding than previous studies, which inadequately addressed the formation and function of carbon-based lubricating films. This research provides a theoretical foundation for the development of high-temperature greases with superior lubrication properties. Peer review The peer review history for this article is available at: Link to website of publons.
Wang et al. (Thu,) studied this question.