Sequential Combination of Femtosecond Laser Ablation and Induced Micro/Nano Structures for Marking Units with High-Recognition-Rate

This study reported the sequential combination of femtosecond laser ablation and induced micro/nano structures on the titanium alloy and nickel-based alloy for laser marking. The preliminary optimization of processing parameters of laser ablation for the marking units is first carried out. The repetition frequency of 50 kHz, the pulse energy of 150 µJ, the scanning speed from 60 to 80 mm s⁻¹, and the groove spacing from 10 to 20 µm are selected as the best processing parameters. Laser-induced micro/nano structures with anti-reflective properties are formed in the primary laser marking zone, which resulted in further improvement in the recognition rate of the markings. For the two alloys, the recognition rate of combined markings is higher than that of primary markings, because the reflectance of the combined markings is lower than that of the primary markings in the spectrum ranging from 380 to 1000 nm. X-ray diffraction analysis showed that the phase constitution of the processed surface is basically consistent with that of the substrate. Moreover, the cracks and re-cast are not observed under metallographic analysis. Therefore, the sequential combination of femtosecond laser ablation and induced micro/nano structures provides a new marking technology with high recognition rate and quality.