Physio-Tribocorrosion Performance of Additively Manufactured Ti6Al4V Alloy in Different Print Directions for Implant Application

Abstract

Additively manufactured (AM) components exhibit orthotropic properties, which can lead to spatial variations in their mechanical properties and functional performance. As a result, implants fabricated using these techniques may also have direction-dependent properties. Therefore, it is very important to evaluate the orthotropic behavior of AM-produced Ti6Al4V (Ti64) alloy for improving the reliability and accurately predicting the service life of such implants. This study investigates the tribological and corrosion properties of scan direction (SD) and build direction (BD) samples manufactured using the direct metal laser sintering (DMLS) technique. Along with different print direction samples, cast-produced Ti64 samples were also tested as a reference. Both the corrosion and tribological characterizations were carried out in phosphate-buffered saline to mimic the human body condition. The tribological property was evaluated using a ball-on-disk tribometer at a sliding speed of 0.157 m/s and a sliding distance of 141.3 m against Al<inf>2</inf>O<inf>3</inf> balls. These tests were carried out at three different 5 N, 10 N, and 20 N loads to gauge the material wear properties in various loading conditions. Apart from this, other characterizations, like microstructural, elemental composition, XPS, wettability, etc., were also performed to understand the wear and corrosion results. The results show that the BD samples possess a lower wear rate (WR) and coefficient of friction (COF) than the SD samples. The microstructural study revealed that this is mainly due to the higher surface hardness and finer grain size. On the other hand, the corrosion rate (CR) was also evaluated using the open circuit potential (OCP) and potentiodynamic polarization (PDP) test. The result shows that DMLS-manufactured Ti64 alloy has lower CR, especially in BD, which is attributed to the formation of a strong passive layer of oxide on the surface. Based on the obtained result, it can be concluded that the DMLS-manufactured Ti64 samples from BD have the highest corrosion and wear resistance due to the higher surface hardness and the presence of a stable oxide layer. Therefore, it can be preferably used in orthopedic applications as compared to both SD and cast-Ti64 alloy. © 2025 Elsevier B.V., All rights reserved.