High power ultra-short pulse laser ablation of IN718 using high repetition rates

Laser ablation using ultra-short pulsed laser radiation with pulse durations below 10 ps is known to be capable of high-precision machining with very small thermal load for the processed workpiece. Although the processing quality is excellent, the productivity is too small for many applications. Therefore, an upscaling of the achievable ablation rate is one major research topic in the field of ultra-short pulse laser ablation. In this study, we identify and investigate a novel high-speed ablation process for the ablation of Inconel 718 using ultra-short pulsed laser radiation. The formation of a thin layer of molten material avoids the formation of rough microstructures on the workpiece surface that usually appear for the processing with high average powers and high spatial pulse overlaps. Thus, processing with high average power of more than 50 W using conventional, high efficient and high flexible beam deflection technology becomes applicable. The presented process is approximately 20 times faster than conventional ultra-short pulse laser ablation with average powers of less than 5 W.The influence of the repetition rate, average power, pulse duration and hatch distance on the high-speed ablation process is investigated. The potential of an optional finishing process to remove the molten layer by melt-free ablation with the same laser system but different processing parameters is demonstrated.