A study on strengthening the corrosion resistance of NiTi SMA by composite femtosecond and nanosecond laser-induced hierarchical micro/nanostructures

A novel method of laser composite processing is proposed to strengthen the corrosion resistance of Nitinol Shape Memory Alloy (NiTi SMA) by combining it with an efficient silanization treatment process. Laser composite processing implies a two-step fabrication process involving femtosecond and nanosecond lasers sequences texturing the surface of the NiTi SMA, resulting in multilayered micro/nanostructures. Compared to the surfaces processed by single laser irradiation, this method further increases the surface roughness of the NiTi SMA substrates. Moreover, the conventional silanization processes have been shown to be effective in reducing the surface free energy after laser texturing. In this paper, superhydrophobic surfaces are prepared on NiTi SMA substrates by employing separate laser and laser composite processing with silanization treatment. The formation mechanism is revealed by scanning electron microscopy (SEM), 3D optical profilometer (OP) and X-ray photo-electron spectroscopy (XPS). The corrosion resistance is illustrated by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. The results show that the multilayered micro/ nanostructures increase the surface roughness and provide more air pockets, laying the foundation for improving superhydrophobicity. In addition, the dense nanostructures formed by femtosecond laser ablation completely isolate the NiTi SMA substrates from the corrosive medium, further improving the corrosion resis-tance. This combination of laser composite processing and silanization process provided an effective method to improve the corrosion resistance of superhydrophobic surfaces.

Automated summary

This paper proposes a novel method of laser composite processing to strengthen the corrosion resistance of Nitinol Shape Memory Alloy (NiTi SMA) by combining it with an efficient silanization treatment process. The method involves femtosecond and nanosecond lasers sequences texturing the surface of the NiTi SMA, resulting in multilayered micro/nanostructures, and further increasing the surface roughness. Superhydrophobic surfaces are prepared on NiTi SMA substrates through separate laser and laser composite processing with silanization treatment. The results show improved corrosion resistance and superhydrophobicity.