Additively manufactured porous Ti–6Al–4V alloy by the PEO/PVD multilayer coatings for enhanced tribocorrosion performance in biomedical applications

This study investigated the corrosion and tribocorrosion performance of laser powder bed fusion (LPBF)-fabricated Ti–6Al–4V gyroid scaffolds, surface-treated with a TiO 2 layer developed via plasma electrolyte oxidation (PEO), followed by a Nb/NbN multilayer coating deposited via physical vapor deposition (PVD). Electrochemical results revealed that the as-built LPBF Ti–6Al–4V scaffolds exhibited lower corrosion resistance than the commercial and LPBF Ti–6Al–4V bulk samples. Surface modification significantly improved corrosion performance. Specifically, PEO-treated and PEO/PVD-treated scaffolds demonstrated ~ 11,000-fold and ~ 1100-fold increases in total resistance compared with LPBF bulk samples. Although the corrosion resistance of PEO/PVD-treated scaffolds was slightly lower than that of PEO-treated counterparts, they outperformed both untreated and solely PVD-coated samples. Tribocorrosion behavior was assessed in a hip simulator using simulated joint fluid and a 15 N load against an Al 2 O 3 ball under open-circuit potential (OCP) and potentiostatic (PS) conditions. Results confirmed that wear was the dominant degradation mechanism. Notably, gyroid scaffolds exhibited enhanced tribocorrosion resistance compared to Ti–6Al–4V bulk samples, with PEO/PVD-treated scaffolds showing the smallest potential drop, lowest corrosion current increase, markedly reduced material loss (~ 81% lower than untreated and ~ 48% lower than PEO-treated samples), and total concentration of released metal ions. In summary, PEO/PVD modification reduced the wear rate of Ti–6Al–4V scaffolds by ~ 80% under PS conditions while maintaining comparable corrosion resistance. These findings highlight PEO/PVD treatment as a promising strategy to increase tribocorrosion performance of additively manufactured Ti-based gyroid scaffolds for demanding biomedical applications.