Numerical Study of Material Selection for Optimal Directed Energy Deposition Single Nozzle Powder Efficiency

Abstract

The efficiency of powder-based directed energy deposition (DED) nozzle is dependent on its ability to direct the pneumatically conveyed powder into the meltpool. Computational fluid dynamics (CFD) with discrete phase modeling (DPM) has been used to investigate the optimization of DED nozzle geometry and DED parameter selection, however, the effect of material choice for nozzle fabrication has not been fully investigated. To explore the effects of the nozzle material on powder efficiency a CFD DPM model was created and analyzed in ansys fluent. Various nozzle materials were simulated using statistical models for the coefficient of restitution (COR) between the powder and nozzle wall from the literature. The results of the CFD DPM model aligned well with experimental data for a 316L stainless steel prototype nozzle. CFD DPM results indicated that using a material with a lower mean COR value improved the powder efficiency of the nozzle. Powder efficiency improved because the component of powder velocity normal to the direction of gas flow was reduced in nozzles made from materials with lower COR values, which in turn led to fewer impacts between the particles and the nozzle walls.