Effect of build direction in Ti6Al4V alloy manufactured by EB-PBF on the corrosion performance of PEO coatings

Abstract This study investigates the influence of build direction in Ti6Al4V substrates manufactured by Electron Beam Powder Bed Fusion (EB-PBF) on the performance of Plasma Electrolytic Oxidation (PEO) coatings. Because of the inherent anisotropy of additively manufactured alloys, arising from differences in thermal history between the build and transverse directions, surface treatments and coating behavior may vary. To explore this, coatings were produced in a silicate–phosphate (Si–P) electrolyte under different current densities and treatment times. The resulting coatings were characterized in terms of morphology, crystalline phase composition, and corrosion performance. The results show that, although build direction affects the initial voltage response during PEO treatment, its influence on coating thickness and porosity is minimal. X-ray diffraction revealed the presence of both anatase and rutile TiO₂ phases, with anatase formation favored at lower current densities. Importantly, PEO treatment eliminated the corrosion anisotropy observed in uncoated Ti6Al4V manufactured by EB-PBF, leading to uniform protective behavior regardless of build direction. Overall, these findings demonstrate the potential of PEO to enhance the functional performance of additively manufactured titanium alloys for biomedical and aerospace applications. In addition, they underscore the importance of electrolyte composition and process optimization in tailoring surface properties.