Influence of Polishing Orientation on the Generation of LIPSS on Stainless Steel

We report on the influence of different angles between the electrical field of the impinging laser and the polishing direction of linearly polished surfaces on the generation of low spatial frequency LIPSS on stainless steel. The electrical field is rotated in a range of 0° to 90° with respect to the polishing direction and its effect on the orientation and homogeneity of the LIPSS is determined. In addition, the influences of the initial surface roughness and laser parameters such as the laser fluence on the generation of LIPSS are investigated. It can be shown, that the formation of LIPSS is driven by the initial surface roughness. The experimental results lead to the assumption that LIPSS were attracted by the linear grooves caused by polishing. Depending on the used parameter set, the orientation of the generated LSFL formation derived up to a value of 45° against the common predictions. Furthermore, a dependency of the required fluence for LSFL on surface roughness and polishing direction is demonstrated. Particularly, LSFL generated with a low fluence are more attracted by the surface polishing. Continuatively, the results may contribute to a further understanding of the underlying mechanisms involved in the generation of LIPSS. Moreover the results can be useful for producing LIPSS in large-scale for possible applications.