Corrosion and stress corrosion cracking behaviour of additive manufactured Ti6Al4V for biomedical applications

The biomedical alloy Ti6Al4V is widely utilized due to its superior mechanical properties, biocompatibility, and chemical stability. Additive manufacturing techniques enable the customization of medical implants, leveraging biometric measurements. Laser powder bed fusion technique (LPBF), specifically suitable for Ti6Al4V, involves selectively melting metal particles layer by layer using a laser, altering the microstructure compared to traditionally produced materials. Biomedical implants are prone to corrosion when in contact with biological fluids, particularly at the material-biological tissue interface, where surface roughness influences cell integration. This corrosion susceptibility is heightened in stress-prone applications like orthopaedic prostheses or exposure to aggressive ions, e.g., fluoride in toothpaste. This research aims to examine Ti6Al4V's corrosion behaviour at varying surface roughness levels, assessing it through electrochemical polarization techniques (OCP, PD, GS, EIS) in simulated body fluid (SBF). Stress corrosion cracking (SCC) under steady strain was also investigated via microcapillary technique in both SBF and fluoride-enriched saliva solution. Comparative analysis reveals similar corrosion behaviour between conventional and additive manufactured Ti6Al4V, with instances where the latter exhibited enhanced corrosion and SCC resistance. The LPBF material exhibits high corrosion resistance due to a robust, dense passive surface layer. This behaviour is attributed to the denser oxide layer in printed materials, impeding electron passage and enhancing the interface's capacitive behaviour. Ultimately, LPBF-produced Ti6Al4V demonstrates comparable resistance to corrosion-induced failure as conventional titanium alloy, providing assurance regarding its biomedical applications.