Anti-corrosion superhydrophobic surface of LPBF- NiTi alloy fabricated by nanosecond laser machining

Abstract

Laser powder bed fusion (LPBF) of NiTi shape memory alloys expands its application range because it overcomes the shortcomings of traditional processing methods. However, the insufficient surface corrosion resistance limits its further application. To further improve the corrosion resistance of LPBF-NiTi alloy by building superhydrophobic surfaces, in this paper, nanosecond laser machining combined with a grid-like scanning strategy was used to construct micro-nano papillary structures and observed by SEM and LCMS. Meanwhile, by exploring the effect of low-temperature heat treatment time on surface wettability, the superhydrophobic surface was obtained after low-temperature heat treatment for 1 h. XRD, EDS and XPS were used to analyze the effect of chemical composition changes on surface wettability. Ultimately, the difference in corrosion resistance of the surface was tested electrochemically. The results showed that the critical factor affecting the transformation of wettability is the large amount of CC/CH in the air adsorption on the surface, and the superhydrophobic surface contributes to improving corrosion resistance. The polarization tests showed that the corrosion current density (Icorr = 2.92 × 10−8) is much lower than the substrate, about an order of magnitude. And the corrosion potential (Ecorr = −0.31 V) and the polarization resistance (Rp = 281.8 KΩ·cm2) are higher than the substrate.