High-speed observation of melt pool-vapor interactions in long-pulsed laser ablation of metals

Laser ablation of metals can be performed using cost-effective and efficient continuous wave fiber lasers using the fast power modulation capabilities of these beam sources. Single-pulse laser ablation of steel with pulse durations in the microsecond to millisecond time scale is observed using a high-speed camera setup to investigate the dynamic interactions between the generated melt pool and the vapor phase. Distinct processing regimes were identified depending on the pulse duration, temporal pulse shape, and power density. Pulse durations in the microsecond range can lead to beneficial processing conditions for ablation processes. In this regime, phase explosion and dynamic melt expulsion by melt uplift and coaxial droplet ejection due to the rapid drop in vapor pressure after the laser pulses were observed as desirable mechanisms, leading to effective material removal and high processing quality with little melt adhesion.