Microstructure and corrosion behavior of laser powder bed fusion Ti-6Al-4V alloy for orthopedic implant application

Purpose The application of laser powder bed fusion (LPBF) for manufacturing Ti-6Al-4V biomedical implants requires a precise understanding of how specific process parameters affect the material’s corrosion resistance. This study aims to quantitatively determine the relationship between key LPBF variables – laser power, scan speed and hatch distance – and the resulting electrochemical corrosion performance in simulated body fluids. Design/methodology/approach Ti-6Al-4V specimens were fabricated using a designed experimental matrix that varied the LPBF parameters. The corrosion resistance of these specimens was evaluated through a series of electrochemical tests – open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) – conducted in Hank’s Balanced Salt Solution (HBSS) and a 3.5% NaCl solution. Findings The corrosion performance was found to be highly sensitive to the LPBF parameters. Increased laser power and scan speed were directly correlated with a decline in corrosion resistance, which microstructural analysis linked to reduced densification. One specific parameter set, producing Specimen S8, yielded superior results. This specimen achieved a linear polarization resistance of 127,855 Ω·cm² in HBSS and 820,716 Ω·cm² in 3.5% NaCl. Its corrosion current density was minimized to 0.0317 µA/cm² and 0.04719 µA/cm², leading to notably low corrosion rates of 0.07365 mpy in HBSS and 0.1094 mpy in 3.5% NaCl, confirming its exceptional performance. Originality/value This work provides a quantitative framework for optimizing the LPBF process, directly linking specific parameter sets to measurable improvements in the corrosion resistance of Ti-6Al-4V. The findings offer practical guidance for manufacturing implants with enhanced longevity and reliability in the human body, moving beyond qualitative assessments to provide clear, data-driven design criteria.