High-power laser-matter interaction during laser powder bed fusion

Laser powder bed fusion (LPBF) additive manufacturing (AM) is developing with the goal of fabricating parts with high performance and high efficiency. Laser power is the key factor to the efficiency, microstructure and performance in LPBF. However, there are limited reports regarding the laser-matter interaction in LPBF under high-power conditions. In this work, the molten pool characteristics and spatter behavior in LPBF with a high power and a wide process window (from 350 W to 1550 W) are studied based on high-speed high-resolution imaging. The results show that the molten pool characteristics and spatter behavior depend on the laser input energy. The average ejection velocity and ejection angle increase with the laser power. The droplet column ejection and large spatters are prone to occur with a high-power laser. Furthermore, the times at which the vapor depression and the protrusion in the molten pool first occur decrease dramatically with an increase in the laser input energy. When the laser mode and spot size are kept constant, the laser power determines the amount of time required for melting, the vapor depression and the protrusion in LPBF to occur, while the laser scan velocity determines whether the laser dwell time is sufficient for these phenomena to form.