Forward calculation model for utilization of energy and mass in laser-directed energy deposition

Precise control of energy and mass utilization is essential for the process design and optimization of powder-based laser-directed energy deposition (L-DED). However, fully comprehending the actual changes in the energy and the mass, which have complex nonlinear relationships with all inputs, is still challenging. In powder-based L-DED, the energy absorptivity is closely related to the powder catchment efficiency, owing to the effects of the laser incidence angle and the material properties. In this study, a forward calculation model was established for the utilization of energy and mass in powder-based L-DED without data regression of experimental measurements. Interactions between the laser, powders, and substrate were analyzed in detail in terms of three major effects: energy absorption of the substrate, powder catchment, and deposition shape variation. A secondary correction of the incidence angle was included in the geometric change of the deposited passes, and the boundary shift of the molten pool, which resulted from the melting point differences of the dissimilar deposited and substrate materials, was considered. The model prediction results matched the multipass deposition experimental results well. The average prediction error validated that the catchment efficiency did not exceed 5.2%. The scanning speed and the powder feed rate showed the largest effects on the energy absorptivity, which varied in the range of approximately 40-65%. The developed model presents good universality and can be fundamental for understanding the forming mechanism, optimizing the process, and predicting the deposition quality of powder-based L-DED.