In vitro corrosion and biocompatibility behavior of CoCrMo alloy manufactured by laser powder bed fusion parallel and perpendicular to the build direction

Abstract

Biomedical cobalt-chromium-molybdenum alloys (CoCrMo) are frequently used for orthopedic implant and dental materials exposed to mechanical stressors, such as wear and cyclic load. Due to the high demand for customizable implant shapes, these alloys are increasingly manufactured by additive manufacturing methods such as laser powder bed fusion (LPBF). LPBF results in different microstructures and surface roughness as a function of the building direction. This study investigated the corrosion resistance, bioactivity, biocompatibility, and microstructure of LPBF CoCrMo (low carbon content, heat-treated) in the XY (perpendicular) and XZ (parallel) plane of the building direction for as-printed (as-received) and abraded surfaces. A distinct microstructure and different surface roughness were found for the XY and XZ planes. The as-received XY surface showed the lowest corrosion resistance but was still passive in phosphate-buffered saline (PBS, pH 7.4). As-received surfaces were less corrosion-resistant than abraded surfaces. All specimens exhibited lower corrosion resistance in PBS containing citric acid at pH 7.4 than in PBS and citric acid alone. As-received surfaces showed better hydroxyapatite precipitation and cell viability; however, all surfaces had satisfactory biocompatibility and bioactivity. This study showed that the building direction had a minor effect on the corrosion of LPBF CoCrMo. © 2023 Elsevier Ltd