Improvement of tribological properties of Ti6Al4V by nitrogen plasma immersion ion implantation

Plasma immersion nitrogen implantation of Ti6Al4V (TAV) alloy was carried out to improve the surface tribological properties of test samples for artificial heart valves. Our results show that a good implantation with nitrogen peak concentration of 40% was achieved but with only approximately 50 nm implanted layer, after 60 min of treatment. Longer treatments showed no improvement in the retained dose, probably due to sputtering effects. However, both significant reduction of friction coefficient and increase in hardness was seen even for such a shallow implantation. Furthermore, the hardness improvement extended to regions much deeper than the implanted layer. Improvements of the wear resistance of such nitrogen implanted Ti alloy is expected, increasing considerably the useful lifetime of components made of TAV which is finding widespread use in biomedical and aerospace applications.