Fabrication of durable hydrophobic micropatterns on stainless steel using a hybrid irradiation process

Patterns were fabricated on AISI 304 stainless steel combining the wire electric-discharge machining (WEDM) with large pulsed electron beam (LPEB) irradiation to improve the surface hydrophobicity and corrosion resistance of the alloy. The WEDM-fabricated patterns showed a Wenzel-to-Cassie transition with contact angle (CA) of 140° at a groove depth of 250 μm, which indicated hydrophobic surface. LPEB irradiation of the WEDM-fabricated patterns increased the CA (166.7°) to the Cassie state at a lower groove depth of 200 μm. The LPEB-irradiated patterns had smooth surfaces that decreased the critical angle for Wenzel-to-Cassie transition. Attenuated total reflection-infrared spectroscopy revealed that hydrophilic functional groups on the surface were absent following LPEB irradiation. LPEB irradiation modified the surface corrosion resistance of a WEDM-fabricated pattern, likely because of a lower surface energy and formation of a passive resolidified layer following irradiation.