A Pickering emulsion strategy for low-friction and wear paraffin/epoxy phase-transition lubricating composite coating

Although the incorporation of phase-change materials (PCMs) can provide active thermal management to mitigate coating failures induced by frictional heat, the inherent softness of PCMs often limits their ability to enhance the mechanical and wear properties of epoxy-based coatings. Herein, an oil-in-water Pickering emulsion approach was employed to fabricate three types of solid-liquid phase-transition lubricating coatings, using paraffin wax (PW) as the oil phase and various nano-reinforcements (halloysite nanotube (HNT), SiO 2 and TiO 2 ) as stabilizers. This method produced composite coatings with a dense and pore-free microstructure due to its effective control over filler particle size and dispersion uniformity. The effects of emulsion content and various nanofillers on the mechanical properties, interfacial temperature, and tribological performance of the coatings were investigated. The composite coating prepared from 5 g HNT@PW Pickering emulsion exhibited a low friction coefficient (0.075) and low wear rate (9.3 × 10 −7 mm 3 /(N·m)). Even under prolonged sliding (150,000 cycles, 5655 m sliding distance), the coating demonstrated outstandingly stable and durable friction-reduction and anti-wear performance, highlighting its potential for engineering applications. This behavior originates from the combined action of the PW solid-liquid phase transition, forming a lubricating film and reducing interfacial temperature, and the strengthening effect of nanoparticles, which improves mechanical and wear resistance. In contrast, SiO 2 nanoparticles in the corresponding composite coating, despite offering the optimal strengthening effect, acted as abrasives during the friction process, thereby aggravating abrasive wear. This work provides an innovative design for synergistic optimization of thermal management, mechanical integrity, and tribological performance in phase-transition lubricating coatings via Pickering emulsions.