A surface spectroscopic study of nitrogen ion-implanted Ti and Ti-6Al-4V wear against UHMWPE

Nitrogen ion-implanted pure Ti and Ti-6Al-4V alloy femoral heads that had been subjected to wear tests in a joint simulator were analysed by AES and XPS, in order to identify their surface composition and to estimate the amount of wear. XPS and AES survey spectra show that the surface of the ion-implanted specimens consist of mainly a thin (∼10 nm) TiO2 surface oxide. Significant amounts of nitrogen in the form of Ti nitride are detected in spectra from the surface, both prior and after the wear tests. On some of the wear-tested specimens, areas covered by a Ca-dominated surface film of unidentified origin are observed. It is demonstrated how the overlapping Ti and N Auger peaks can be separated so that the nitrogen depth distribution can be obtained in depth profile measurements. The nitrogen depth profiles show that the thickness of the implantation layer varies considerably at different points on the samples. For the commercially pure Ti samples, the total amount of wear is significantly higher than for the Ti-6Al-4V samples. In none of the analysed samples had the ion-implanted layer been worn off completely after the simulation. (author)