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technical paper
The Influence of Ambient Atmosphere on LIPSS Formation in Stainless Steel: A Comparison between Ps- And Ns-Pulse Processing
keywords:
laser-induced periodic surface structures
laser surface engineering
lipss
In this contribution, we investigate the influence of ambient atmosphere on the formation of laser-induced periodic surface structures (LIPSS) on the metal surface using 8 picosecond and 45 nanosecond pulses. We patterned the surface of AISI 216 stainless steel in air, nitrogen, and argon and observed that the properties of the fabricated LIPSS were affected by changing the beam scanning velocity and pulse fluence while keeping the pulse duration constant. The LIPSS phenomenon was found to be strongly dependent on the atmosphere surrounding the irradiation spot during fabrication. When patterned with picosecond pulses, the dependence was less pronounced and manifested itself mainly in the curvature of the fabricated ribs. The spatial period of the fins patterned with picosecond pulses was smaller in air than in nitrogen and argon atmospheres. On the other hand, periodic structures were observed with nanosecond pulses only when laser processing was performed in air, suggesting that the structures were related to surface oxidation. Further analysis using EDS, XPS, AFM, and FIB cross sections revealed that LIPSS obtained with nanosecond pulses on samples consisted mainly of periodic parallel ridges of accumulated oxides, while in the case of picosecond pulses LIPSS consisted of topographically modulated bulk material with an oxide layer deposited uniformly over the entire surface of the sample. The results suggest that the formation of stainless steel LIPSS is significantly influenced by the surrounding atmosphere and the pulse duration used for laser processing.