Ultrafast Laser Texturing of Stainless Steel in Water and Air Environment

Abstract

Ultrafast laser texturing allows the generation of micro- and nanostructures on steel substrates. Laser-ablated textures show a wide range of structure geometries, from the micro to the nanoscale, which can enable plastic product functionalization. Polymer processing technologies are used to replicate mold textures on a large manufacturing scale. To enable new product functionalities, developing novel texture geometries is critical. The laser-ablated texture dimensions are primarily linked to the laser light properties, such as the laser wavelength, thus limiting the achievable structure shapes. This work uses ultrafast laser to manufacture textures in air and water environments. The effect of the different mediums on structures formation is characterized. The irradiation is performed over a wide range of fluence values. The texture geometry and characteristics are evaluated by scanning electron microscopy. For decreasing fluence values, the structures transitioned from micro bumps, to LIPSS, to nanostructures, regardless of the irradiation environment. Conversely, structure morphology is affected by the irradiation environment. The LIPSS pitch is lower for the underwater environment due to the change in the laser angle of incidence, which changes with the refraction index ratio of the air and water. A novel nano-lamellae texture was generated when irradiating the steel surface underwater at relatively low fluence. The dynamics of different LIPSS generations are discussed, considering the irradiation medium’s optical, thermal, and physical properties.

Scanning Strategies in Laser Surface Texturing: A Review

“…It is mentioned that the local frost layer around the laser-irradiated spot melts into water, helping to boost ablation efficiency, suppress the recast layer and reduce the heat-affected zone, while the remaining frost layer can prevent ablation debris from adhering to the target surface. The frost layer eliminates the debris deposition and recast layer, and LIPSS formation has a mechanism similar to high-spatial-frequency (HSF) LIPSS formation in water [ 124 , 125 ].…”

Wear Resistance Improvement of Alloy Steel Using Laser Surface Treatment

“…The volume shift that occurs during the transformation of austenite to martensite is linked to the creation of residual stresses, also a favorable compressive stresses due to the surface transformation by laser pulses; however, when those pulses are overlapped, the microstructure in the overlapped region is tempered, and residual stresses become tensile. In the heat-impacted zone, however, overlapping laser passes resulted in a more homogeneous microhardness distribution with acceptable surface roughness [10,11].…”

Wetting Characteristics of Laser-Ablated Hierarchical Textures Replicated by Micro Injection Molding

“…Femtosecond laser sources can be integrated into CNC machines, allowing for the ablation of complex mold surfaces [30]. Moreover, controlling the laser texturing parameters allows for generating micro-and nano-scale features with the same equipment in a one-step process [31,32]. This allows for significant advantages over other technologies, such as those that rely on masks (i.e., limits on the feature size) or those requiring a clean room environment (e.g., EBM).…”