The Impact of Intra-Burst Energy Distribution on Volume Removal and Surface Quality in Laser Ablation of Stainless Steels Using Ultrashort Pulsed Lasers

Stainless-steel alloys are widely used in applications requiring high corrosion resistance and mechanical durability. For embossing tool fabrication, high-volume material removal with high surface quality is essential. Laser-based ablation offers an alternative to micromilling by enabling material removal without mechanical contact, thereby eliminating cutting tool wear and facilitating the fabrication of complex geometries. However, productivity must be increased without degrading surface quality, which plays a critical role in embossing tool wear behavior and lifetime. This study investigates the ablation efficiency and surface quality of AISI 304, AISI 420, and AISI 316Ti stainless steels using a 250 fs pulsed laser. Different fluence levels and burst configurations, including MHz, GHz, and Bi-burst, are examined, focusing on the influence of intra-burst energy distribution on material removal rate and surface quality. Surface morphology and roughness are characterized by optical, confocal, and scanning electron microscopy. The results show that removal rate, ablation efficiency, and surface roughness are strongly affected by the intra-burst energy distribution (positive or negative slopes). The highest removal rate of 5.74 mm3 min−1 was obtained using MHz bursts, whereas GHz bursts enabled surface roughness values Sa below 1 µm. Negative energy slopes generally reduced surface roughness in isolated MHz and GHz burst modes, while Bi-burst processing provided smooth surfaces over a wider range of slope conditions. All alloys followed similar trends, with AISI 316Ti exhibiting greater susceptibility to microhole formation under certain burst conditions.