Corrosion and Tribocorrosion Resistance of Superhydrophobic Lpbf-Niti Alloys Surface Fabricated by Nanosecond Laser and Ultrasonic Fluorination

Abstract

NiTi alloys have been extensively studied for their excellent super-elasticity (SE) and shape memory effects (SME). With the development of laser powder bed fusion (LPBF), it is possible to process the complex structure of NiTi alloy, which results in the mechanical property of LPBF-NiTi alloys receiving great attention. However, the processing method is different from the traditional one, which not only has an impact on the mechanical properties but also seriously affects the anti-corrosion resistance and caused a substantial deterioration. In the research work of this paper, nanosecond laser processing was used to fabricate the bionic mastoid-shaped micro-nano structure on the LPBF-NiTi alloys. An efficient and convenient ultrasonic fluorination treatment was used to achieve the full surface coverage of FAS-17 in 10 minutes, and the superhydrophobic LPBF-NiTi alloy surface (CA~157°) was successfully achieved. The constructed superhydrophobic LPBF-NiTi alloy surface exhibits excellent anti-corrosion resistance compared with the original surface, and the Icorr from (4.42±0.5)×10-7 A·cm-2 reduced to (3.21±0.5)×10-10 A·cm-2. Meanwhile, the superhydrophobic surface showed excellent surface stability no matter in the 15-day immersion experiment or in the tribocorrosion test under extreme environments. The remarkable anti-corrosion resistance and stability of the superhydrophobic surface can be attributed to the micro-nano structure rich in the TiO2 oxide layer, the air layer formed by the superhydrophobic surface insulates the corrosive liquid and the stable hydrophobic agent film.

Keywords: Ultrasonic fluorination, Nanosecond laser, superhydrophobic, Anti-corrosion, Tribocorrosion, LPBF-NiTi alloy