An investigation on the powder recycling effect on the processability of Ti6Al4V alloy via DED process

The objective of this work is a feasibility study on recycling the Ti6Al4V alloy powder used for the production via Direct Energy Deposition (DED) and an investigation on the effects on the processability. The powders analysed are first collected from a deposition tank after DED printing of an additive piece and then mechanically sieved to restore their original granulometry range of 45-106 µm. The second step has involved a comparison between virgin and recycled powders via SEM looking for oxidation, impurities and shape defects. Then new printing parameters have been searched through a DoE method to study the relationship between laser powder, scanning speed, hatching distance and layer height. Finally, the new settings have been used to print the samples for studying the mechanical properties through a tensile test. The analysis show that Ti6Al4V DED’s powders after one loop of recycling do not show relevant oxidation and impurities although the granulometric distribution is slightly different. Consequently, process parameters are changed facing a significant increment of Volumetric Energy Density. In conclusion, it has been pointed out that is possible to reuse titanium powder in a 100% recycled mix without affecting the overall quality of the printed object but with an increase of the printing time and a consequent reduction in productivity.