Plasma nitriding behavior of Ti6Al4V orthopedic alloy

The influence of plasma nitriding on mechanical, corrosion and tribological properties of Ti6Al4V has been investigated using X-ray diffraction, microhardness tester, scanning electron microscopy, pin-on-disc tribotester, electrochemical polarization and impedance spectroscopy. Plasma nitriding treatment of Ti6Al4V has been performed in 25%Ar-75%N-2 gas mixture, for treatment times of 1-4 h at the temperatures of 650-750 degrees C. The corrosion tests were carried out in Ringer solution at 37 degrees C, and the wear tests were performed in dry sliding conditions. XRD analyses confirm the formation of delta-TiN and tetragonal epsilon-Ti2N phases in the modified layer. It was observed that the surface hardness and wear resistance increase as the treatment time and temperature increase. The electrochemical impedance measurements indicate a decrease in double layer capacitance value and increase in charge transfer resistance for the nitrided specimens compared to the untreated ones. (C) 2007 Elsevier B.V. All rights reserved.