Nanodiamonds for improving lubrication of titanium surfaces in simulated body fluid

Abstract
Hip implants are often made from titanium or titanium-based alloys. However, wear during the operation inside the human body is a key source of implant failure and adverse health effects. We propose new insight on the lubrication of titanium components. Addition of small amounts (less than 0.2 wt%) of nanodiamonds (NDs) to simulated body fluid promotes a substantial improvement in friction (3 times reduction) and wear (up to 2 orders of magnitude wear reduction) behavior of the titanium surfaces. Interestingly, the amount of NDs needed for improvement of friction and wear characteristics is critically dependent on the applied loads. With higher contact loads, larger concentrations of NDs are needed for better friction and wear reduction. Analysis of the wear track formed during sliding indicates the formation of a carbon-rich tribolayer which improves tribological properties of the contacting surfaces. Our results suggest that the carbon layer is formed from the nanodiamonds embedding in the top layer of titanium.