Energy Density Comparison via Highspeed, In-situ Imaging of Directed Energy Deposition

Abstract

Metal additive manufacturing has become an increasingly popular technology and receives interest from multiple business sectors that require optimally lightweight components and mass customization (aerospace, automotive, and medical device). Directed energy deposition (DED) is one of the main laser-based additive manufacturing processes, but a fundamental understanding of the process is lacking partly because it has not been the focus of highspeed, in-situ x-ray imaging studies like laser powder bed fusion has. A novel in-situ DED system is presented here, and an experimental study is performed to show that the small-scale system recovers processing parameter trends of a full-scale build. Observed meltpool lengths range from about 200 μm to 900 μm, while meltpool depths range from about 50 μm to 500 μm and can support high-fidelity modelling. Additionally, an investigation on the relationship between meltpool dimensions and global energy density GED' is performed. It was found that GED' is not a good predictor of meltpool dimensions due to the discrepancy in linear and exponential trends in laser powder and powder mass flowrate. Further studies and analysis using the presented novel DED system are needed to develop an appropriate energy density term to predict of meltpool dimension and clad height.