Effect of infrared nanosecond pulse laser polishing on surface quality, microstructure, and corrosion behaviour of additively manufactured Ti–6Al–4V alloy

Abstract Additive manufacturing (AM) enables the fabrication of complex Ti–6Al–4V components for biomedical applications, yet surfaces produced by electron beam powder bed fusion (EB-PBF) and laser-based powder bed fusion (LB-PBF) typically exhibit high roughness and surface defects that compromise corrosion performance. Conventional continuous-wave laser polishing can reduce their roughness, but it often induces microstructural changes that degrade the properties of AM alloys. This study demonstrates that infrared nanosecond-pulsed laser polishing provides an improved surface quality and corrosion resistance free of microstructural modification. EB-PBF and LB-PBF Ti–6Al–4V samples were polished using an infrared nanosecond pulsed laser and evaluated in terms of surface roughness, microstructure, and corrosion behaviour in simulated body fluid. Laser polishing reduced surface roughness by up to 38% for EB-PBF (from Sa ~ 40 to 25 µm) and 25% for LB-PBF (from Sa ~ 12 to 9 µm), while exhibiting a localised modification of the microstructure. Electrochemical testing revealed a significant increase in passive film breakdown potential (ΔE = 1.901–2.001 V for EB-PBF and 1.800–1.900 V for LB-PBF), accompanied by a reduction in passive current density of approximately 85% for EB-PBF and 40% for LB-PBF. EB-PBF samples displayed the highest breakdown potential after polishing (2 V). Overall, nanosecond laser polishing is a promising method for improving the surface integrity and corrosion resistance of AM Ti–6Al–4V components for biomedical applications.