Optimizing Laser Ablation of Stainless Steels for Volume Removal and Surface Quality Using Burst of Pulses

Stainless steel alloys are widely used in industrial applications requiring high corrosion resistance and mechanical strength. In many of these applications, laser-based surface processing is utilized for modification, enhancement, or functionalization of the material. However, laser processing is strongly influenced by the alloy's chemical composition, thermal diffusivity, and microstructural characteristics. This study examines the ablation efficiency and surface quality of ablated volumes in AISI 304, AISI 420, and AISI 316Ti steel alloys under ultrashort pulsed laser (250 fs) at various fluence levels and burst configurations (MHz, GHz, and Bi-burst). Key performance parameters, including ablation rate, surface roughness (Sa), structure isotropy, and morphology are evaluated using optical, confocal, and scanning electron microscopy methods. The results indicate that MHz bursts substantially enhance ablation rates (e.g., from 1.5 to 3.2 mm3 min-1 at 9 J cm-2) and ablation energy efficiency (e.g., from ≈1.4 to 2.75 μm3 μJ-1 at 9 J cm-2) compared to standard pulsed mode. Furthermore, GHz bursts can achieve superior surface quality (Sa ≈ 0.5 μm) but with lower ablation rates (0.7 mm3 min-1). Finally, Bi-bursts can balance the performance, reaching moderate ablation rates (3.2 mm3 min-1) with intermediate roughness (Sa ≈ 2 μm). The results show similar trends across all alloys but highlight AISI 316Ti's susceptibility to microhole formation, which is influenced by the pulse energy distribution.