Electrochemical and bioactive characteristics of the porous surface formed on Ti-xNb alloys via plasma electrolytic oxidation

Abstract

This study examined the capability of plasma electrolytic oxidation (PEO) to fabricate an ideal implant porous material for bio-implant applications. For this purpose, the Ti-xNb binary alloys (x = 10, 30, and 50 wt.%) were treated via PEO using a DC power supply at a voltage was fixed to be 280 V for 180 s using an electrolyte composed of calcium acetate and calcium glycerophosphate. The structure of Ti-xNb alloys before PEO was altered from needle-like structure to an equiaxed structure with increasing the Nb content. After PEO, the high content of Nb element in the substrate led to an increase in the size and fraction of the micropores where a highly porous coating was fabricated on the sample with 50 wt.% Nb. This was attributed to the high plasma discharges developed at high current density conditions. The coating made on Ti-30Nb alloy exhibited a high ratio of Ca/P and higher corrosion resistance as compared to the counterparts formed on Ti-10Nb and Ti-50Nb alloys. The presence of anatase and Nb2O5 together with ∼1.13 μm micropores in the coating made on Ti-50Nb alloy were the main factors responsible for the easy formation of hydroxyapatite during the soaking in a simulated body fluid solution.