Enhanced Tribocorrosion Resistance of Hard Ceramic Coated Ti-6Al-4V Alloy for Hip Implant Application: In-Vitro Simulation Study

Developing coatings for various applications is an area of research of uttermost importance, to protect surfaces from severe damage by improving the wear and corrosion resistance of the materials. Recently, there has been increasing interest in ceramic coatings for biomedical applications, as the surface may become more inert in nature for the biological reactions and potentially increase the lifespan of the implants and minimize the side effects on the patients. Hence this study is focused on the tribocorrosion behavior of the ceramic coatings for the hip implant application on commonly used implant titanium alloy. The three types of the ceramic coatings are conventional monolithic micron alumina (IDA), micron alumina-40 wt % yttria-stabilized zirconia (YSZ) composite coating (IDAZ), and by-layer nanostructured alumina-13 wt % titania/YSZ (IDZAT) on Ti-6Al-4V alloy. A series of tests, under free potential and potentiostatic mode, were conducted using a hip simulator tribocorrosion setup under simulated joint fluid (bovine calf serum with protein concentration 30g/L). The tribological conditions are pin-on-ball contact with a load of 16N (approximately contact pressure of 50 MPa), the frequency of 1 Hz (walking frequency), and with an amplitude of 30°. The tribocorrosion studies clearly revealed that the coatings have better wear and corrosion resistance and the predominant damage mechanism was mechanical wear rather than corrosion. Among the coatings, the IDZAT shows enhanced tribocorrosion performance by exhibiting more positive OCP, no induced current, and a lower coefficient of friction.