Robust macroscale superlubricity of multiple base oils achieved on soft epoxy resin coatings

Steady macroscale superlubricity was firstly achieved on epoxy resin coating lubricated by multiple base oils including nonpolar and polar oils. Hydroxylated tribofilm on counter balls lubricated by multiple base oils was observed by TOF-SIMS spectra. [Display omitted] •Steady macroscale superlubricity was achieved on epoxy resin coating lubricated by multiple base oils.•No obvious run-in stage to superlubricity for the steel/epoxy resin tribopairs lubricated by different base oils.•Soft epoxy resin coating performed superior wear resistance under oil lubrication.•Hydroxylated tribofilm on the counter balls lubricated by multiple base oils was observed by FTIR and TOF-SIMS spectra. Reducing the friction of base oils to a superlubricity state is highly expected at engineering scale. However, it still is a great challenge for the most of viscous base oils to achieve superlubricity on the conventional tribopairs up to now. Here we report the strategy of solid-oil composited lubrication constructed with an ultra-smooth epoxy resin (EP) coating and base oils for achieving superlubricity. Especially, the frictional results showed that the proposed strategy in this study could be suitable for multiple base oils, including nonpolar and polar base oils as lubricants. The friction coefficient of steel/EP tribopair lubricated by the base oils containing hydroxyl group can be as low as 0.001. Meanwhile, the composited lubrication system did not undergo an obvious running-in stage to achieve the superlubricity state regardless of the type of base oils. The surface hydroxylation of the steel counter ball sliding against EP coating was observed by time-of-flight secondary ion mass spectrometer, even when lubricated by nonpolar base oils without hydroxyl group. This could be a critical factor for the base oils to achieve superlubricity. This finding provides a new and facile approach to realize robust superlubrication for different base oils at engineering scale.