Analysis of the Influence of Shielding and Carrier Gases on the DED Powder Deposition Efficiency for a New Deposition Nozzle Design Solution

In Direct Energy Deposition of metal parts the powder deposition efficiency is defined as the ratio of the nominal metal powder feed rate to the amount of powder directly involved in the component manufacture. Generally, the powder particles falling into the molten pool represent only a small portion of the total amount of metal particles nominally provided by the feeding system (less than 50% for most of the commercial systems), deteriorating the process performances in terms of powder waste, production time and increasing the production costs. For constant laser power, laser scan speed, and laser spot diameter, the deposition efficiency is primarily associated to the nozzle geometry, feeding system, and powder characteristics (e.g. particle size distribution, particle shape and size).

The current work focuses on the analysis and characterization of the performances of a new generation of high efficiency nozzles with an enhanced design which adopts the inert Argon gas for a double purpose of Shielding and Carrier. The proposed analysis consists in designing and executing an experimental campaign structured as a full factorial Design of Experiments to map the impact of Shielding gas, Carrier, and Ti-6Al-4V powder mass flow on the deposition efficiency by monitoring the resulting geometry of the powder flow. A numerical CFD simulation is also carried out to verify the possibility in deducing a control logic to modulate the aforementioned process parameters on a custom feeding system demonstrator. The metal powder and the benefit of the approach are assessed with regards to an industrial use case.