Increase of surface hardness induced by O, Ca or P ion implantation into titanium

Titanium or titanium alloys are very attractive materials for use as biomedical materials. Non-toxic elements of oxygen, calcium and phosphorus were implanted into titanium and the changes of surface hardness were measured using an ultra microindenter (UMIS-2000) with the multiple load–unload procedure. Depth profiles of implanted ions were obtained by SIMS measurement. O implantation resulted in the greatest improvement in hardness, up to 2.2 times higher than the unimplanted titanium at the peak. Ca implantation did not improve the hardness as much. The cause may be the formation of a glass-like layer of CaTiO3 and TiO2 on the surface. For P implantation, the depth of maximum hardness increased with increasing implantation energy. The depth of the peak hardness was approximately one-third to one-eighth of the projected range of the implanted ions.