Metal corrosion causes huge economic losses and major disasters every year. Inspired by the lotus leaf and nepenthes pitcher, the superhydrophobic surfaces (SHS) and the slippery liquid-infused porous surfaces (SLIPS) were produced as a potential strategy to prevent metal corrosion. However, how to prepare stable water-repellent coatings that can prevent the intrusion of corrosive ions remains to investigate. In this work, we first fabricated a micro/nano hierarchical structure on the aluminum surface by femtosecond laser processing. Then, the SHS was prepared on the above structure by fluorosilane modification. Finally, the SLIPS was fabricated on the SHS by coating lubricant. The morphology and wettability of the fabricated samples were evaluated by scanning electron microscopy and contact angle measurements. Furthermore, the corrosion resistance properties of SHS and SLIPS in simulated seawater were characterized by electrochemical measurements. From the comparison of the electrochemical parameters of different immersion times, both water-repellent coatings are effective in protecting the aluminum alloy from corrosion in simulated seawater due to reduced contact area between the metal substrate and corrosive solution. In comparison with the SHS, the SLIPS has a corrosion inhibition efficiency of up to 99.95% and it maintains long-term stability in the corrosive solution. This work also provides a promising method for the water-repellent coatings by femtosecond laser processing for metal corrosion prevention in practical industrial applications.

In this work, both numerical simulations and experimental characterization were used to obtain a broad understanding of the thermo-mechanical history, residual stress, and microstructure of the directed energy deposition (DED) process of austenitic stainless steels. To investigate the effect of process factors on residual stress, the global sensitivity analysis approach based on D-MORPH-HDMR was utilized. The results of the research reveal that the amplified effect of the influence of the three input variables (layer thickness, L; laser power, P; and scanning speed, v) on the transverse residual stress and thickness-direction residual stress is L > P > v; in contrast, the influence of longitudinal residual stress is P > L > v. We also found that general tendencies in local plastic strain accumulation are analogous to the relative distribution of geometrically necessary dislocations (GNDs). Additionally, we investigated post-solidification structures connected to residual stress, such as submicron dislocation cells and dynamic recrystallization (DRX) in austenitic stainless steels during DED. The investigation revealed that the DDRX and CDRX phenomena were caused by the bulging of initial grain boundaries and progressive sub-grain rotation (PSR). The fact that the sample bottom had more thermo-mechanical cycles than the top led to a higher dislocation density and hence more DDRX. This study presents a unique perspective on the link between residual stress and microstructure in additive manufacturing.

Continuous-wave laser (CW) and pulsed-wave laser (PW) are the two laser modes in direct energy deposition (DED). This paper mainly reports on a study into the effects of the two laser modes on residual stresses with a given energy input. The contour method (CM) with non-uniform spatial distribution of inspection points was used to capture residual stress distributions in DED of Fe3000 on a substrate made of 316L stainless steel. Residual stresses in the transition zone between the deposit and the substrate were carefully examined to gain an understanding of cracks frequently observed at the connection between the substrate and the deposit. Furthermore, X-ray diffraction, along with successive material removal, was used to reveal residual stresses at various depths in the substrate. The results showed that significant tensile longitudinal stresses developed at the substrate–deposit junction for both CW and PW laser modes. It increased sharply (about 64%) with the increase in energy input for CW mode, while it showed the opposite trend for PW mode; the longitudinal residual stress decreased 13.2% with the increase in energy input. PW, however, introduced lower residual stress than that of CW under the condition of high-energy input; the maximum longitudinal residual stress decreased by about 10.4% compared to CW mode. This was due to stress relaxation at high-energy inputs in PW mode. In addition, residual stresses were found to be higher than the initial yield stress, and yielding occurred in the deposited part. The results determined by the CM and X-ray diffraction depth profiling were found to be consistent.

The epitaxial growth of dendrites, which often results in a strong texture, is the most common phenomenon during the laser additive manufacturing process. In this study, the epitaxial growth of dendrites and texture evolution in three directions were studied by changing the z-increment, pulse period, and track offset, respectively. The influence of the molten pool interface on the growth and competition of dendrites is analyzed. Both green grains ( // BD) with rotated cube texture in the molten pool overlapping zones and red grains ( // BD) with fiber texture in the molten pool center zones coexist for different z-increment samples, forming the typical sandwich texture feature. In a short pulse period, the dendrites can grow directly epitaxially and form the strong fiber texture due to gentle interface and short distance. With the decrease of the track offset, the molten pool morphology changes from flat to narrow and deep. When θ is close to 90°, dendrites grow along the secondary dendrite arms at the overlapping zone, forming V-shape grains. This work also provides a promising method for texture customization for laser additive manufacturing.

Slippery lubricant-infused surfaces (SLIPS) suffer from rapid lubricant depletion, severely limiting their durability in practical applications. To overcome this, we propose a laser-engineered hierarchical architecture that physically locks a solid paraffin lubricant, creating a multifunctional coating with thermally switchable slipperiness. Using femtosecond laser ablation, a hierarchical porous structure (HPS) was fabricated on an aluminum alloy, followed by silanization to achieve superhydrophobicity (contact angle ≈ 154.7°) for enhanced paraffin wetting. The resulting HPS-P coating exhibits thermally switchable adhesion: water droplets pin on the solid surface (sliding angle > 90°) but slide readily (<10°) upon heating above the paraffin’s melting point. The coating demonstrates rapid self-healing, repairing severe scratches within 100 s via molten paraffin flow. The HPS-P coating provides excellent corrosion protection, with its corrosion current density reduced by six orders of magnitude compared to bare aluminum and an inhibition efficiency approaching 100%. This work provides a durable, thermally responsive coating strategy with integrated anti-corrosion and self-healing functions for extreme environments.