High-repetition-rate femtosecond laser processing affected by heat accumulation effects for precision surface patterning of titanium

• The ablation threshold of pure titanium decreases from 20.5 mJ/cm 2 to 8.9 mJ/cm 2 with an increased laser repetition rate from 100 kHz to 1 MHz. • The heat accumulation effect analysed by two temperature model fits well with the fact in experiments of a decreased threshold and intensified heat affected zone when the laser repetition rate increases from 100 kHz to 1 MHz. • Optimization of laser repetition rate parameters for precious surface patterning is ought to balance the processing threshold and quality • Scanning strategies can modify the depth of laser-induced ablation craters to some extent. Titanium, with its essential applications in aerospace and biomedical engineering, poses significant challenges for precision surface structuring due to its high corrosion resistance and high-temperature stability. This study addresses micrometer-scale surface patterning requirements for titanium through systematic investigation of high-repetition-rate femtosecond laser machining. As the laser repetition rate increases from 100 kHz to 1 MHz, the ablation threshold decreases by a factor of two, accompanied by a substantial expansion of heat affected zone. At fixed laser parameters, higher scanning speeds enhance the machining depth with negligible degradation of the quality. Theoretical analysis based on the two-temperature model reveal the influence of repetition rate on ablation threshold, demonstrating an effective heat accumulation with roughly 10 mJ/cm 2 @1 MHz laser injections. This research advances the understanding of the interaction mechanisms between titanium and high-repetition-rate femtosecond laser, thus providing valuable insights for the developing of high-precision surface processing techniques for titanium-based materials.