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.
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.
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.
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.
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