The influence of energy density in selective laser melting on TNT-coated Ti6Al4V: corrosion resistance and biocompatibility insights

Ti6Al4V alloys were fabricated using a selective laser melting (SLM) method at different energy densities. Afterward, TiO2 nanotube (TNT) films were deposited on the surfaces of these substrates via anodization to investigate the effect of energy density on the resulting TNT structures. According to results, the high-energy–density SLM sample exhibited a relative density (RD) exceeding 98.8%, representing the highest RD among all the fabricated samples. Moreover, the smallest nanotube diameter and the greatest film thickness were obtained from the anodization of the substrate with the highest relative density, which was a result of being fabricated at the highest energy density. Electrochemical tests revealed significant improvements in corrosion resistance for TNT-coated samples compared to untreated Ti6Al4V. The TNT-coated Ti6Al4V sample fabricated at the highest SLM energy density (A2) exhibited the highest corrosion potential (Ecorr = −1.24 V) and the lowest corrosion current density (Icorr = 56 × 10⁻⁸ A/cm2), while untreated Ti6Al4V (A1) showed Ecorr = −1.74 V and Icorr = 303 × 10⁻⁷ A/cm2. Biological evaluations demonstrated that TiO₂ nanotube (TNT) coatings significantly enhanced the biocompatibility and antibacterial properties of Ti6Al4V surfaces, particularly for the A2 sample. Fluorescence staining, MTT assays, and nuclear staining confirmed that A2, which featured reduced nanotube diameter and increased length, supported superior osteoblast adhesion, proliferation, and viability, while also exhibiting the strongest antibacterial activity against E. coli. These improvements were attributed to the optimized nanotopography, which promoted cell interaction and inhibited bacterial adhesion. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.