Abstract
Surface texturing of metallic surfaces is studied in mixed regimes of ablation and melting, by adjusting time and energy
distribution of infrared lasers, for textures combining ablated and elevated topography in relation to the original surface.
This can allow for higher productivities and a wider range of geometries than purely ablative micromachining LST.
A methodology is presented for producing regular patterns of micron sized features on metals. By adjusting scanning
patterns, features well under the beam size can be obtained, resulting from the displacement of the molten bath by the
intense recoil pressure generated by the ablated metal. By engineering the flow of the bath and the position of the recast
material, very high aspect ratio structures can be obtained, with limits very dependent on the characteristics (viscosity,
temperature, ...) of the molten bath. 2-5 microns sized walls, 40 microns high, were obtained with nanosecond laser of
50 microns beam diameter on titanium. Sub-nanosecond laser pulses were also studied: passively q-switched lasers with
400-500 ps pulse length provide very precise control of molten pool displacement and fine feature generation.
Ni-Cr and Ni-Cu coated steel was textured in the form of two dimensional square textures and ribletted surfaces, in order
to evaluate the molten metal flow, the progressive shaping of the textures and the redistribution of the layer components
during the process.
