Influence of wetting pinning on lubrication performance of bionic fluted structural surface under oil rich condition

Abstract

Controlling the internal friction of lubricating oil films is crucial for reducing friction power loss, enhancing mechanical efficiency, and extending component service life. Natural organisms precisely regulate the dynamic behavior of liquids and gases through surface hydrophilic and hydrophobic pinning. Inspired by the natural widespread fluted structures, fluted structural surfaces (FSS) were fabricated using 3D printing. Through surface self-assembly and spraying methods, after oleophobic modification, the FSS were investigated how the orientation, groove spacing, and surface oleophobicity of these structures affect lubrication performance and the underlying mechanisms. The vertical-oriented fluted structure exhibits a lower friction coefficient due to a wedge effect, while an appropriate groove spacing further optimizes lubrication performance. Surface wettability significantly affects the lubricating performance of FSS. Under a load of 25 N and a reciprocating frequency of 7.5 Hz, the friction coefficient of the superoleophobic FSS (SoFSS) decreased by 58.3 % and 49.5 % compared to the oleophilic non-textured/textured surfaces, respectively. The results show that the superoleophobicity within the fluted grooves and the oleophilic wetting pinning at their tips enhance the formation and stability of the gas layer within the grooves, thereby synergizing and enhancing the hydrodynamic pressure effect to achieve gas-liquid mixed lubrication. This study provides a new insight for the design of advanced lubrication materials under complex operating conditions.