Biomimetic Fabrication and Self-Lubricating Tribological Performance of Laser-Textured Solid-Liquid Composite Coatings

To address the problems of poor lubrication film stability and insufficient lubricant supply under limited-oil conditions, this study proposed a novel strategy of biomimetic design combined with magnetically controlled lubrication for synergistic enhancement in solid-liquid composite coatings. By employing picosecond laser etching on the surface of magnesium alloy, biomimetic Nepenthes-inspired crescent-shaped oil storage structures and iris-inspired wedge-shaped directional transport structures were fabricated. These were integrated with a sprayed molybdenum disulfide (MoS₂) solid lubricant coating and a magnetorheological fluid (MFS) lubricant to construct a self-lubricating, magnetically tunable, multi-scale composite coating (L-Mg@SMP/MoS₂@MFS). Tribological tests showed that under a rotation speed of 200 r/min and a load of 5 N, the composite coating reduced the friction coefficient by 90% (down to 0.057) compared to the substrate, and wear mass loss decreased by 47%. With the introduction of a 350 mPa·s MFS, the coating's lifespan increased by 200%. Mechanism analysis revealed that the crescent-shaped structures enabled lubricant recirculation via oil storage and pressure gradient-driven replenishment, while the wedge-shaped structures promoted directional lubricant transport through Laplace forces (24 μm/s). Magnetic field regulation further enhanced oil film stability through the aligned arrangement of Fe₃O₄ nanoparticles (average size about 50 nm), achieving a centrifugal retention rate of over 85%. This study offered a new biomimetic-magnetic synergistic approach for long-lasting friction reduction design under limited-oil lubrication scenarios.