Investigation on anisotropic tribological properties of superhydrophobic/superlipophilic lead bronze surface textured by femtosecond laser

[Display omitted] •The lead bronze samples after ultrafast femtosecond laser-treated had high surface polar bond content and free energy, making the initially hydrophilic surface more hydrophilic and turned into a superhydrophilic surface.•After two months of exposure to the air, the adsorption of hydrocarbons on the surface increased the content of C-C/C-H non-polar bonds, which presented superhydrophobic/superoilphilic characteristics•Superhydrophobic/superhydrophilic surfaces had different tribological properties under oil lubrication and dry friction, although there mainly occurred fatigue wear. Superhydrophobic and superlipophilic surfaces have been widely used in rail transit, petroleum equipment, aerospace, and other fields in recent years. Most of these surfaces have the disadvantage of poor wear resistance. However, the surface of the suitable microstructure has antifriction and wear-resistant properties. The femtosecond laser is easy to control, has good repeatability, and has great advantages in preparing special wetted surfaces with microstructures. In this work, an ultrafast femtosecond laser is used to prepare a superhydrophobic/superlipophilic lead bronze surface. It is found that the sample immediately after laser processing has a high content of surface polar bonds and high free energy, which is a super-hydrophilic surface. After being placed in the air for two months, the adsorption of hydrocarbons on the surface increases the C-C/C-H non-polar bond content, and the surface free energy decreases, showing superhydrophobic/superlipophilic characteristics. The friction behavior of superhydrophobic/superlipophilic surfaces in oil lubrication and dry friction is different, and the anisotropy of the surface structure will also lead to the anisotropy of the tribological properties. There mainly occurred fatigue wear. This work provides a method for the preparation of anisotropic antifriction and wear-resistant superhydrophobic/superlipophilic surfaces, and variable surface microstructures could be prepared for various friction conditions.