Investigation on the Potential of Laser and Electron Beam Additively Manufactured Ti-6Al-4V Components for Orthopedic Applications

In the present study, corrosion properties and biocompatibility of as-built and as-polished Ti-6Al-4V samples fabricated by Electron Beam Melting (EBM) and Selective Laser Melting (SLM) were investigated and compared with a conventional sample as a reference. Optical microscope, Scanning Electron Microscope equipped with Energy Dispersive Spectroscopy, and X-ray diffraction analysis were employed for studying the microstructure and composition of the samples. Polarization, electrochemical impedance, and immersion tests were carried out to investigate the corrosion behavior and bioactivity of the samples in the Simulated Body Fluid solution. The results revealed that the EBM samples exhibited a superior corrosion resistance compared to the SLM one, thanks to the absence of low corrosion resistant alpha' martensitic phases and a higher fraction of beta phase in the EBM samples. It was also observed that while the wrought Ti-6Al-4V samples had a higher corrosion current density than the additively manufactured ones, both EBM and SLM processes had a lower corrosion resistance in the as-built state than in the as-polished. The immersion tests in the SBF solution revealed a more significant bioactivity for the EBM samples than the SLM samples. Higher levels of the beta phase in the EBM microstructure stimulated the nucleation and growth of the apatite on the sample surface. Also, higher surface roughness in the as- built samples improved the bioactivity by increasing the metal/ electrolyte interface and thus forming more OH- groups on the Ti alloy surface.