This paper reports on nanocharacterization of commercial Ti-6Al-4V and sintered Ti-Si-B alloys after surface treatment by high temperature plasma immersion ion implantation (HTPIII) to investigate fatigue in addition to hardness and wear properties. The results show that HTPIII is an effective method for improvement of the mechanical and tribological properties of the conventional Ti-6Al-4V alloy, however higher temperatures are necessary to produce the same gain on sintered Ti-Si-B alloys. For the Ti-6Al-4V sample after HTPIII the SIMS experiments identify a nitrogen-rich layer with a thickness of about 1 ?m. The untreated samples show a barely visible nitrogen signal below the surface oxide, indicating a large nitrogen uptake and retention during the HTPIII process. Both HTPIII treated alloys presented higher hardness and wear resistance, but – surprisingly - lower fatigue resistance.
