Corrosion and Tribocorrosion Behavior of Ti-40Nb and Ti-25Nb-5Fe Alloys Processed by Powder Metallurgy

The requirement of good mechanical properties, lower Young's modulus, superior corrosion resistance, and excellent biocompatibility makes beta-type titanium alloys attractive materials for orthopedic implants. In this study, Ti-25Nb-5Fe and Ti-40Nb beta-type titanium alloys were designed and produced by powder metallurgy route using titanium hydride, niobium, and iron powders. The effect of sintering conditions on microstructure, corrosion, and tribocorrosion behavior was explored. Electrochemical behavior was investigated in saline solution (9 g/L NaCl) at body temperature by using potentiodynamic polarization and electrochemical impedance spectroscopy. Tribocorrosion behavior was evaluated by reciprocating against an alumina ball at open circuit potential, as well, under anodic and cathodic potentiostatic conditions in saline solution (9 g/L NaCl) at body temperature. The physical, electrochemical, and tribo-electrochemical behaviors of both alloys were improved with increasing sintering time at 1250 degrees C from 2 to 4 hours and decreasing Fe particle size for Ti-25Nb-5Fe alloy. Degradation under tribocorrosion conditions was mainly governed by mechanical wear on Ti-25Nb-5Fe alloy; however, Ti-40Nb alloy exhibited an antagonistic effect between corrosion and wear during testing under anodic applied potential due to the formation of a denser tribolayer.