Formation of Laser-Induced Periodic Surface Structures on Titanium Alloy Using a Picosecond Laser: Dependence on Fluence and Number of Laser Pulses

Laser ablation is a widely used technique for the fabrication of periodic structures on solids to manipulate their surface properties. A fundamental challenge in the formation of laser-induced periodic surface structures (LIPSS) is ascertaining the correlation between laser parameters and LIPSS characteristics. This study focuses on the characterization of LIPSS in terms of the period of low spatial frequency LIPSS (LSFL) and their homogeneity as a function of single pulse fluence and effective fluence dose in the range from 0.067 to 1.070 J cm-2 and from 50 to 1280 J cm-2, respectively. Here, a 1064 nm laser with a pulse duration of 13 ps was utilized to create LIPSS on Ti6Al4V alloy. The morphology of the formed structures was analyzed using the two-dimensional fast Fourier transform method applied to scanning electron microscopy images. Homogeneous LSFL with spatial periods are obtained for effective fluence doses of 50 and 160 J cm-2. However, an increase in the effective fluence dose up to 640 J cm-2 led to the formation of so-called large LIPSS and the disappearance of homogeneous LSFL. The evolution of LIPSS that has been observed is attributed to changes in the ratio and absolute values of the ablative and heating components of the laser pulse energy at different single and effective fluence doses. Our study contributes to the development of tailored surfaces with periodic structures on Ti alloys.