Atomistic insights into ultrafast laser-induced local structural dynamics and wettability modulation in austenitic stainless steel 316L

This study investigates the nanostructural evolution of austenitic stainless steel 316L subjected to ultrashort laser irradiation through a hybrid computational approach combining classical molecular dynamics and the two temperature model. Two distinct irradiation regimes are explored: (i) a low-fluence regime which is characterized by various defect formations mainly, including twin boundaries, stacking faults, and dislocation networks. (ii) a higher fluence regime where pronounced surface roughening emerges, with an optimal laser dose leads to the generation of nanobump structures as key features. A clear mechanism for the origin of these resulting nanobumps, as a combined effect of liquid stretching, rapid resolidification, and stress confinement dynamics, is established. Importantly, a direct link between the local surface wettability and laser fluence is proposed. We show that controlled laser energy deposition enables the selective local functionalization of stainless steel surface wettability to achieve either hydrophobic or hydrophilic behavior. • Atomic-scale view of femtosecond laser texturing of 316L steel. • Nanobump formation mechanism revealed by hybrid TTM-MD modeling. • Defect generation and surface roughness control local wettability. • Laser fluence precisely tunes surface from hydrophilic to hydrophobic. • Direct link between atomic-scale dynamics and wettability.