Nitrogen assisted formation of large-area ripples on Ti6Al4V surface by nanosecond pulse laser irradiation

Ti6Al4V is one of the most widely used titanium alloys due to its excellent mechanical, physical, and chemical properties. Laser surface texturing is a promising method to endow new functions of material surfaces; however, direct generation of laser-induced periodic surface structure (LIPSS) on the Ti6Al4V surface by nanosecond laser is rarely reported. In this study, by nanosecond laser irradiation in nitrogen atmosphere, the ripples (a typical LIPSS) were directly fabricated on the Ti6Al4V surface. By single-line laser scanning, the effects of laser irradiation parameters including the laser power and repetition frequency on the formation and evolution of the ripples were systematically investigated, followed by optimizing the laser irradiation parameters to achieve the large-area regular and clear ripples with relatively good surface quality as well. Furthermore, by performing contrast experiments in argon atmosphere, the role of nitrogen atmosphere on the formation of ripples was confirmed. Accordingly, formation mechanism of the ripples was discussed. Finally, the effects of the formed ripples on the surface color and wettability were preliminarily characterized to demonstrate the potential applications of surface ripples. This paper provides a nitrogen assisted method to fabricate large-area ripples on the Ti6Al4V surface by nanosecond laser irradiation.