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Abstract—Durable color laser markings on stainless steel are attractive for traceability, product authentication, and identification of industrial components exposed to mechanical contact. In this work, the scratch-test response of nanosecond fiber-laser-marked AISI 304 stainless steel was evaluated for a 7 × 7 processing matrix. The laser-marking parameters were: average power P = 3–15 W and hatch spacing Δx = 40–100 µm, while the scanning speed, pulse repetition rate, pulse duration, and scanning strategy were kept constant at 100 mm/s, 500 kHz, 8 ns, and two passes (0°/90°), respectively. Scratch testing was performed with a CSEM REVETEST system using a Rockwell-type diamond indenter (tip radius 200 µm, cone angle 120°) under a progressive load from 0 to 30 N, with scratching oriented transverse to the raster direction. For all 49 conditions, the coefficient of friction µ and tangential force Ft were compared at a normal load Fn = 20 N and were benchmarked against the untreated surface.
The untreated reference exhibited µ = 0.259 and Ft = 5.20 N. The most severe friction response was observed at P = 3 W and Δx = 40 µm, where µ increased to 0.406 (+56.7%). The lowest friction values were obtained at P = 3 W, Δx = 70 µm (µ = 0.225) and at P = 15 W, Δx = 100 µm (µ = 0.225), corresponding to reductions of about 13.2% relative to the untreated condition. Small hatch spacings (40–60 µm) required higher laser power to reduce friction, whereas Δx = 70 µm provided a comparatively stable low-friction window across the full power range. The results show that tribological response can be tuned by balancing interline overlap, local remelting, and the fraction of untreated surface retained between laser tracks.