Discrete Phase Modeling of the Powder Flow Dynamics and the Catchment Efficiency in Laser Directed Energy Deposition With Inclined Coaxial Nozzles

Abstract

Laser Directed Energy Deposition (DED) is one of the most promising additive manufacturing processes for restoring high value components. The damaged components can have complex free-form shapes which necessitates depositions with an inclined nozzle, where, the gravity can adversely affect the powder flow dynamics and the powder catchment efficiency (PCE). PCE is defined as the fraction of the total mass flow rate entering the melt pool and a low PCE can render the process inviable. In this paper, the effect of nozzle inclination on the powder flow dynamics and resulting PCEs have been studied. It was found that the powder flow dynamics is altered significantly in an inclined nozzle and results in an asymmetric and skewed powder jet. This affects the powder focusing adversely and the PCE deteriorates rapidly with an increase in the inclination and falls below 20% at 75°. A discrete phase model has been developed to understand the powder flow dynamics at different inclinations and process conditions. The mass flow distribution asymmetry on the focal plane at various nozzle inclinations have been analyzed via the model. The model is able to predict PCEs at different nozzle inclinations with reasonable accuracy. It has been observed that carrier gas flow, particle size and laser diameter affect the PCE significantly and can be used to counter the enhanced powder loss at large nozzle inclinations. Process maps have been developed to identify the favorable, acceptable and low PCE regions for the selection of optimal DED parameters.

Energy Efficiency in Additive Manufacturing: Condensed Review

“…Ahn et al [27] explored and deliberated upon the principles, optimization parameters, and practical applications, as explained in Figure 10, an electron beam is directed toward a plate or substrate material where it impinges with a wire or powder feedstock material and melts, leaving deposits of material on the bed. Further, in a study [28] Alya et al examined the effect of nozzle rotation on the dynamics of powder flow and the associated powder catchment efficiency, and the relation was discussed and examined from an energy point of view. It was found that an angled nozzle drastically changes the mechanics of the powder flow, producing an uneven and asymmetric powder jet, so it was proved that nozzle parameters are directly proportional to the parameters discussed.…”

Investigation of molten pool geometry and flow field based on powder scale modeling in laser directed energy deposition

“…The second type of LDED numerical model considers powder delivery and is recognized as a powder-scale model [18][19][20]. In this model, the powder handling approach can be categorized into two types based on the level of computational accuracy.…”