Corrosion Assessment of Wrought and Additive Manufactured Ti-6Al-4V and Co-Cr-Mo Alloys

Ti-6Al-4V and Co-Cr-Mo alloys are frequently used as biomedical implants due to their excellent mechanical, electrochemical properties, and biocompatibility. Additive manufacturing (AM) through Selective Laser Melting (SLM) is a revolutionary materials processing method for layer-by-layer creation of parts or prototypes directly from a CAD file. Therefore, SLM of Ti-6Al-4V and Co-Cr-Mo alloys presents a unique opportunity to design implants completely specific to patient’s specific clinical application. As opposed to the conventional manufacturing methods consisting of slow and controlled thermal changes, SLM involves rapid thermal changes, first heating and melting the alloy powder followed by rapid cooling at high cooling rates (quenching). This difference in fabrication method has shown to have an impact on the mechanical properties and microstructure. Many studies have been performed on the corrosion properties of wrought Ti-6Al-4V and Co-Cr-Mo, however not much is known about the corrosion properties of the SLM alloys. SLM and wrought manufactured Co-Cr-Mo and Ti-6Al-4V alloys are purchased to assess differences in corrosion performance. Potentiodynamic (PD), Potentiostatic (PS), and Electrochemical Impedance Spectroscopy (EIS) are employed electrochemical corrosion techniques to determine the corrosion differences in pH 4,7,10, and physiological PBS solution. After each experiment, the microstructure is analyzed using scanning electron microscopy (SEM) and optical microscopy (OM) to assess the corrosion-induced damage on the surface and identify corroded phases in the alloys. In case of CoCrMo system, there no significant difference in the electrochemical response but after the test some microstructural differences are visible. But for TAV, neither electrochemical nor microstructural differences are observed after the electrochemical tests. The long-term effects of corrosion are assessed with PS tests in which no substantial differences are found between the wrought and the SLM manufactured alloys. Lastly, the development and properties of the oxide are determined using EIS, which showed small differences in the oxide stability between the wrought and SLM manufactured alloy. This implies that the oxide development in wrought and SLM manufactured alloys are similar.