Ion implantation and thermal nitridation of biocompatible titanium.

Nitrogen implantation and thermal nitridation processes are investigated to improve the wear resistance of titanium medical devices. Ion implantation uses 80 keV nitrogen ions and doses ranging between 1 x 10(17) and 5 x 10(17)/cm2 to modify the surface layers up to 140 nm depth. Stable surface layers are obtained at high ion doses by post-annealing at 550 degrees C for 30 min. Thermal processes are developed as a function of the time (20-90 min) and annealing temperature (950-1100 degrees C) in a dry nitrogen atmosphere. The amount of titanium nitride formed during the thermal process increases with the annealing temperature and time. Samples are analysed by Rutherford Backscattering Spectroscopy (RBS), Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM). Ion implantation and thermal nitridation processes increase the surface hardness and wear resistance improving the mechanical properties of titanium used for movable devices for total joint replacements, such as the hip and knee protheses.