Selectable surface nitridation of titanium using focused pulsed Nd:YAG laser irradiation with nitrogen gas blow

• Formation of titanium nitride layer on Ti using laser irradiation was demonstrated.
• The laser used was focused low-power pulsed Nd:YAG laser.
• Laser irradiation was carried out accompanied by nitrogen gas blow.
• Surface hardness of laser-irradiated Ti was five times that of untreated Ti.
• The treatment also enhanced the cell attachment performance of the substrate.

In the present study, we demonstrated that a surface nitride layer with high surface hardness and good cell attachment performance could be produced on an arbitrary area of a titanium (Ti) substrate by using focused pulsed Nd:YAG laser irradiation accompanied by nitrogen gas blow. A focused laser beam induced nitrogen plasma in the vicinity of the Ti substrate surface. This plasma made it possible to form a nitride layer with a sufficient thickness, even when the laser power was low. The produced surface layer was approximately 1100 nm in thickness and was composed of TiN and Ti; the concentration of TiN eventually decreased with increasing depth. The hardness of the laser-treated surface was approximately 7.5 GPa, which was approximately five times that of the untreated Ti surface. Furthermore, the surface wettability of the Ti substrate was drastically improved by treating it with focused laser, which enhanced the cell attachment performance of the substrate. We concluded that the surface nitriding process using focused pulsed Nd:YAG laser is an excellent surface modification technique for Ti materials that can simultaneously improve their wear resistance and cell attachment performance.