Melt pool analysis in DED–LB/M with freeform beam shaping based on high-speed imaging

Abstract In laser-based directed energy deposition of metals (DED–LB/M) the use of conventional Gaussian beam profile can lead to excessive energy input and unstable melt pools due to high intensity in the beam center. These instabilities result in significant fluctuations of the thermal boundary conditions during solidification, which can adversely affect microstructure formation and part quality. Therefore, innovative beam shape sources are being explored, such as static profiles, stepwise adaptable profiles and freeform beam shapes. The aim of this work is, therefore, to explore high-speed optical monitoring data in directed energy deposition using freeform beam shapes. Manufactured single melt tracks are used to explore different beam shapes in terms of laser–material interaction, energy density distribution, melt pool stability and solidification. The evaluation focuses on static intensity distribution and transient changes in between a sequence of images. The evaluation of high-speed camera data allows deriving metrics to evaluate the melt pool stability using the standard deviation, the laser–material interaction zone using a long-term intensity distribution, and the intensity gradient to evaluate the solidification. The melt track width derived from monitoring data matches well the physical measurements of the melt track.