Abstract: NiTi alloys produced using laser powder bed fusion (LPBF) technology have garnered significant attention in the biomedical field due to their high degree of freedom forming, shape memory effect, and superelasticity, showing great potential for various applications. However, current research primarily focuses on designing porous structures to reduce elastic modulus, optimizing process parameters to enhance mechanical properties and functional characteristics, while neglecting surface corrosion resistance. Yet, corrosion resistance in simulated body fluids is crucial for medical applications. This study primarily investigates the impact of scanning speed on corrosion resistance during laser processing. Six groups of samples with varying scanning speeds (100 mm/s, 400 mm/s, 700 mm/s, 1 000 mm/s, 1 300 mm/s and 1 600 mm/s) are analysed. The microstructure, density, and phase composition of the samples are meticulously examined using XRD, OM, SEM, EDS and DSC. Furthermore, the short and long-term corrosion resistance of the samples is assessed through electrochemical testing and immersion testing. The study demonstrates that the scanning speed significantly impacts the corrosion resistance of the sample. The corrosion resistance is closely linked to factors such as the volume fraction of the B19' martensitic phase, pores on the sample surface, and unfused pores. Notably, the sample scanned at 700 mm/s exhibits the highest corrosion resistance, with a corrosion current density of (2.6±0.6)×10⁻⁷A/cm². Long-term immersion experiments reveal that spherical pores generated at low scanning speeds and unfused pores at high scanning speeds are more susceptible to corrosion. Conversely, samples scanned at 700 mm/s and 1 000 mm/s display fewer surface defects, with the surface corrosion products of the 700 mm/s samples showing greater resistance to corrosion damage. This research sheds light on the impact of scanning speed on corrosion resistance, offering valuable insights for the advancement of corrosion-resistant biomedical LPBF-NiTi alloy.

Key words: laser powder bed fusion, NiTi alloy, scanning speed, corrosion resistance, simulated body fluids