集油拒水润滑轨道的脂润滑增效研究OA

Reliability and long-term protection are critical parameters for the operation of marine equipment,where key components such as bearings frequently operate under harsh environmental conditions characterized by high humidity and inevitable seawater intrusion.Under seawater-intrusion conditions,all greases suffer lubrication degradation.While existing tribological studies have explored various methods to mitigate lubricant starvation under limited oil supply conditions or to enhance the water resistance of lubricants separately,there remains a distinct lack of comprehensive strategies that simultaneously address the critical issues of lubricant replenishment and the active prevention of seawater contamination within the contact zone.To address these dual challenges effectively,the work aims to propose a novel composite functional surface design that synergizes femtosecond laser-induced micro-textures with a superhydrophobic polytetrafluoroethylene(PTFE)coating to achieve significant grease lubrication enhancement under seawater intrusion conditions.The experimental methodology involved the utilization of femtosecond laser ablation technology to fabricate comb-tooth-shaped arrays on GCr15 bearing steel surfaces,where the specific geometric dimensions of the textures were optimized to 1.2 mm in length,0.2 mm in width,and 0.2 mm in spacing,with a minimumdepth of 1 μm.Following the precision texturing process,a 30 μm-thick PTFE film was applied to cover the textured area and selectively ablated into the texture grooves to create a functional composite surface.With a custom-built optical interference elastohydrodynamic lubrication(EHL)test rig,the seawater intrusion was simulated by introducing artificial seawater droplets near the lubrication track and the central oil film thickness and oil pool distribution dynamics were monitored via the optical interference method.A comparative analysis was also conducted on the film-forming of polyurea grease and lithium-based grease under these contaminated conditions.Experimental results indicated distinct differences in the water resistance of the greases,with polyurea grease exhibiting superior film-forming performance compared to lithium-based grease under seawater intrusion,a behavior attributed to the denser fiber network structure of the polyurea thickener which effectively resisted water penetration and structural degradation.In contrast,the lithium-based grease suffered from significant film thickness reduction,dropping by 30%to 50%at a speed of 4 mm/s,due to the dilution effect and severe shear thinning caused by 10 μL seawater ingress.Crucially,the proposed composite texture array displayed a unique dual-function capability of water repellency and oil replenishment that functioned as a fluid diode.The low surface energy of the PTFE coating ensured that seawater droplets maintained a Cassie-Baxter contact state with high contact angle of 163° and extremely low adhesion.Driven by the Laplace pressure gradient generated by the asymmetric comb-tooth-shaped geometry,these water droplets were rapidly repelled from the lubrication track at a maximum driving speed of 323 mm/s,a high-speed response that effectively prevented water from entering the Hertzian contact zone and causing emulsification.Simultaneously,inside the texture grooves,the femtosecond laser-induced periodic surface structures and micro-grooves significantly increased surface roughness and wettability for the lubricant,resulting in an oil contact angle of 39°,which created strong capillary forces that actively captured released oil and directed it back into the contact zone.This oil-replenishment mechanism,combined with the water-repellent barrier,effectively delayed the onset of starvation and maintained a stable lubricant supply.Comparative analysis revealed that the composite texture surface prevented water interference and enhanced the oil film thickness by up to 4 times compared to ordinary smooth surfaces under identical seawater intrusion conditions.Furthermore,full-bearing validation tests confirmed the practical efficacy of this design,showing that when the composite texture was applied to both sides of the bearing raceways,the frictional torque was reduced by approximately 68%compared to non-textured bearings,demonstrating stable lubrication performance even at high rotational speed.In conclusion,the comb-tooth-shaped composite texture successfully realizes a synergetic mechanism that actively repels intruding seawater while efficiently recycling lubricant,thereby significantly enhancing lubrication reliability,maintaining stable oil film thickness,and reducing friction torque in marine environments.