Fretting tribocorrosion properties of anodized TiNbSn implant alloy

Abstract

Titanium and its alloys have poor wear resistance, and the biological response to generated wear debris leads to aseptic loosing and pathological bone resorption. In the fretting wear of artificial hip joints, a significant part of the wear surface is contacted by elastic deformation, and electrochemical anodization is a promising method to control the mechanical properties of the surface and improve wear resistance. To suppress wear debris generation and metal ions elution from implant materials into body fluids, the tribocorrosion properties of a newly developed anodized TiNbSn implant alloy were evaluated in the presence of simulated body fluid and compared to those of pure Ti. During anodization under high voltage, spark discharge occurred due to dielectric breakdown occurred for the TiNbSn electrode, but not for the Ti electrode. The primary phase of the anodic oxide layer on TiNbSn alloy was rutile TiO2, whereas that on Ti was anatase TiO2. The anodic oxide layer on TiNbSn had a higher thickness, roughness, and surface area than that on anodized Ti. In addition, the hardness and exfoliation strength were higher than those of Ti. The coefficient of friction of anodized TiNbSn in fretting tests was similar or slightly lower than that of anodized Ti, and the open circuit potential remained unchanged for anodized TiNbSn but shifted to a more negative voltage for anodized Ti. The results suggest that the hard and strongly-adhered rutile TiO2 on TiNbSn formed by spark discharge during the high-voltage anodization process improves fretting wear resistance and reduces the generation of wear debris and elution of metal ions.