Correlation between forming quality and spatter dynamics in laser powder bed fusion

Laser powder bed fusion (LPBF) has broad application prospects due to its high fabrication accuracy and excellent performance, but the dynamic mechanical properties of LPBF components are relatively low due to defects of the melt track such as protrusions and depressions, whose generation mechanisms remain unclear. In this work, we investigate the correlation between the ex situ melt track properties and the in situ high-speed, high-resolution characterization. We correlate the protrusion at the starting position of the melt track with the droplet ejection behaviour and backward surging melt. We also reveal that the inclination angles of the depression walls are consistent with the ejection angles of the backward-ejected spatter. Furthermore, we quantify the vapour recoil pressure by in situ characterization of the deflection of the typical forward-ejected spatter. Our results clarify the intrinsic correlation of the melt track properties, which is important for the stable LPBF formation with few defects.