Characteristics and control of femtosecond laser-induced periodic surface structures

Femtosecond laser-induced periodic surface structures (LIPSS) can significantly enhance the wear resistance, wettability, and self-cleaning capabilities of metallic materials, providing a novel approach for functional surface modification. This study systematically investigates the effects of laser fluence, spot overlap rate, and scanning passes on the morphological characteristics of LIPSS on 1Cr18Ni10Ti stainless steel. Experimental results indicate that under multi-pulse conditions, increasing the laser fluence enlarges the dimensions and periodicity of low-spatial frequency (LSFL) LIPSS, but excessively high fluence degrades the uniformity or even damages high-spatial frequency (HSFL) LIPSS. Increasing the spot overlap rate induces a morphological transition of LIPSS from stripe-like HSFL to a composite structure of HSFL/LSFL, ultimately forming aggregated LSFL clusters with expanded dimensions. Additional scanning passes mimic the effect of higher fluence while improving HSFL distribution uniformity without structural damage. In single-pulse experiments, the spatial period of LIPSS decreases radially from the spot center, and the central period increases with higher fluence, revealing the coupling mechanism of surface structuring and melting effects. These findings provide critical theoretical support for the morphological control of LIPSS, advancing the application of femtosecond laser technology in aerospace materials.