In Vitro Tribocorrosion Evaluation of Carbide-derived Carbon (CDC) for Hip Implants.

Carbide-derived carbon (CDC) was previously proposed as a surface modification method for hip implant applications since it showed excellent tribocorrosion performance under open-circuit potential (OCP) conditions. Nonetheless, a systematic evaluation of CDC's tribocorrosion properties was still missing. Therefore, our objective is to test CDC's tribocorrosion performance under various electrochemical conditions and to identify the synergism between wear and corrosion. Based on the findings, the variations in OCP for CDC (0.626 mV) is smaller than Ti6Al4V (1.91 mV), and CDC showed lower induced current than T6Al4V for all potentials, suggesting CDC is more stable than Ti6Al4V under tribocorrosive conditions. Eventually, the weight loss of Ti6Al4V (50.662±5.19 µg) was found to be significantly higher than that of CDC (4.965±5.19 µg), which agrees with the electrochemical results. In summary, CDC showed better tribocorrosion performance than Ti6Al4V and was determined as an Antagonism regime.

Fretting-corrosion Apparatus with Low Magnitude Micro-motion (≤5 µm): Development and Preliminary Outcome.

Fretting-corrosion is one of the failure processes in many applications, including biomedical implants. For example, the modern design of hip implants with multiple components offers better flexibility and inventory storage. However, it will trigger the fretting at the implant interfaces with a small displacement amplitude (< 5 µm) and usually in a partial slip region. Although many studies have been reported on the fretting, they have high displacement amplitude and are in the gross slip region. It is imperative to have an apparatus to overcome such limitations, specifically for hip implant applications. Therefore, this study describes the development of a fretting-corrosion apparatus with low micro-motion (≤ 5 µm) that can simultaneously monitor the corrosion process. Initial experiments with Ti6Al4V-Ti6Al4V in 0.9% saline, Ti6Al4V-Ti6Al4V in bovine calf serum (BCS), and ZrO2-Ti6Al4V in BCS were conducted to validate the system. As a result, the fretting regime of all groups remained partially slip region throughout the 3600 cycles, and the possible failure mechanisms are proposed in this manuscript.

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.