Femtosecond laser-induced micro/nanostructures facilitated multiple passivation and long-term anti-corrosion property of laser powder bed fused Ti-6Al-4V alloy

The formation of non-equilibrium phases and microstructural defects reduces the passivation performance and corrosion resistance of laser powder bed fusion (LPBF) produced Ti-6Al-4V alloy, threatening its safe service as important components. This work aims to enhance the corrosion resistance of LPBF-produced Ti-6Al-4V alloy through femtosecond laser surface processing (FLSP). FLSP at lower powers (<300 mW) or higher powers (>400 mW) creates uniform layers of periodic nanostructures and hierarchical micro/nanostructures on the alloy surface. The prolonged exposure to air significantly accelerates the oxidation of Ti2+ to Ti4+ on FLSP-induced micro/nanostructures, resulting in multiple passivation behaviors and remarkable improvement in corrosion resistance.