Modeling and experimental analysis of energy attenuation and partitioning during laser based direct energy deposition

Energy attenuation and partitioning are important phenomena during laser-material interaction in laser based direct energy deposition (DED). They have immediate impact on molten pool thermal history and thus affecting the quality of the fabricated part. In this paper, a lumped capacity model was developed to analyze the energy attenuation and partitioning in DED for Inconel (IN) 718 fabrication. Energy absorption and reflection by powders and substrate, energy loss due to radiation and convection as well as latent heat of fusion were quantified based on experimental analysis. High-resolution infrared camera was used to measure the temperature of the molten pool. The energy attenuation by the powders was measured by a power meter. The results suggest that the energy attenuation coefficient of IN 718 in DED is 6.13 % when laser power is 250 W. Also, it is concluded that about 36.3 % of the laser energy is absorbed by the substrate, only a small amount of energy (less than 1 %) is lost due to radiation and convection.