Fig. 1. Picosecond laser processing system

Fig. 2. Schematic of picosecond laser scanning path. (a) Horizontal scanning; (b) vertical scanning; (c) repeating region of horizontal scanning route and vertical scanning route; (d) overlap region of horizontal and vertical scanning route

Fig. 3. Surface morphologies of samples under different laser fluences. (a) 0 J/cm2; (b) 1.39 J/cm2; (c) 4.95 J/cm2; (d) 6.85 J/cm2; (e) 10.21 J/cm2; (f) 12.42 J/cm2

Fig. 4. SEM images of different regions at laser fluence of 6.85 J/cm2. (a) Edge portion of pit; (b) columnar protrusion; (c) bump at bottom of pit

Fig. 5. 3D morphologies and cross-sectional profiles of as-prepared sample surfaces at laser fluence of 6.85 J/cm2. (a)(b) Overall 3D morphologies; (c)(d) local 3D morphologies; (e)(f) cross-sectional profiles

Fig. 6. Contact angle and sliding angle versus laser fluence. (a) Contact angle; (b) sliding angle

Fig. 7. Water droplets on nickle-aluminum bronze alloy surface. (a) Water droplet on polished nickel-aluminum bronze alloy surface (left) and superhydrophobic nickel-aluminum bronze alloy surface (right); (b) water droplets on nickel-aluminum bronze alloy surface with a sliding angle of 90°; (c)-(e) dynamic decomposition diagram of water droplet contacting with superhydrophobic nickel-aluminum bronze alloy surface

Fig. 8. SEM images of sample surfaces under different processing conditions. (a) Polished sample surface; (b) sample surface modified with stearic acid after polishing; (c) picosecond-laser-processed surface at laser fluence of 6.85 J/cm2; (d) stearic acid modified sample surface processed by picosecond laser at laser fluence of 6.85 J/cm 2

Fig. 9. XRD plots of superhydrophobic nickel-aluminum bronze alloy surfaces

Fig. 10. Polarization curves of different samples

Fig. 11. Contact angle and sliding angle versus time

Table 1. Laser processing parameters

Table 2. EDS of nickel-aluminum bronze alloy surfaces at different treatment stages