Study on bio-tribological properties of nitrogen ion implanted UHMWPE

As the aseptic loosening induced by polyethylene wear debris is the main cause of long-term failure of total joint replacements, increasing the wear resistance of ultrahigh molecular weight polyethylene (UHMWPE) will be very important to obtain long-life artificial joint. In this paper the UHMWPE was implanted with 450 keV N+ ions to three doses of 5x10(14)/cm(2), 2.5x10(15)/cm(2) and 1.25x10(16)/cm(2). The friction and wear behaviors of UHMWPE were studied under lubrication of distilled water and blood plasma using a ball-on-disk tribometer with a ZrO2 ceramic ball as a counterface. Experimental results showed that the friction coefficient of ions implanted UHMWPE are higher than un-implanted UHMWPE. Under blood plasma lubrication condition, the wear rate of implanted UHMWPE was lower than un-implanted UHMWPE, and the wear rate decreased with increasing implantation dose. The plow, plastic deformation and fatigue were wearing mechanism for un-implanted UHMWPE and the abrasive wear for implanted UHMWPE.