Tribocorrosion properties of different type titanium alloys in simulated body fluid

Abstract

Body fluids and relative motion between implant and bone lead to synergistic degradation reactions, which cause failed implantation or adverse tissue reactions for implant materials used in human body. Because of their good chemical biocompatibility as well as acceptable mechanical properties, titanium (CP Ti) and its alloys are widely used in implant applications. β-type Ti alloys including alloying elements such as Nb, Zr and Mo have become more popular among the extensively used α- and (α+β)-type Ti alloys due to their low elastic modulus, comparable mechanical properties and high biocompatibility. This paper was mainly aimed to investigate the electrochemical and tribological properties of β-type Ti alloys. Also, traditionally used α-type Ti (α- CP Ti) and (α+β) type Ti-6Al-4V (α/β- Ti64) alloys were included for comparing the same set of the results. The XRD and SEM investigations and hardness measurements were utilized to analyze the structure, surface morphology and mechanical behavior of the alloys. Simulated body fluid (SBF) was used as corrosive environment. Tribocorrosion tests were carried out at open circuit potential (OCP), cathodic and three different anodic potentials under reciprocating sliding condition. Potentiodynamic scans were obtained with and without wear test. Friction coefficient, current density and volume loss were measured and calculated. The relative motion accelerated the material loss in corrosive environment due to the combined effect of electrochemical reaction and tribological action. All Ti alloys had almost the same sensitivity to the potentiodynamic corrosion. The ratio of depassivation/repassivation affected wear performance of titanium and its alloys during tribocorrosion tests. The rate of chemical reaction was higher in β-type Ti-15Mo (β- Ti15) and Ti-45Nb (β- Ti45) alloys as compared to others. The (α+β) type Ti-6Al-4V (α/β- Ti64) and β type Ti-13Nb-13Zr (β- Ti1313) showed lower volume loss and lower friction coefficient values during tribocorrosion tests than others. The corrosion resistance of the β- Ti64 alloy exhibited better corrosion resistance than β- Ti1313 alloy. However, considering the implants applications, the β- Ti1313 alloy may be a good candidate with relatively low elastic modulus and without toxic alloying elements. © 2015 Elsevier B.V.