The impact of Ti6Al4V powder reuse on the quality of electron beam powder bed fusion parts

The electron beam powder bed fusion (PBF-EB) process has several advantages typical of additive manufacturing. However, at the end of the process, a large amount of powder is left that needs to be disposed of. Therefore, reusing powder for several build jobs may represent an interesting opportunity in the context of sustainable manufacturing. On the other hand, the reused powder differs from the virgin one in terms of chemical–physical characteristics due to the thermal history experienced in previous build jobs. As a consequence, the possible effects on the quality and mechanical properties of final PBF-EB parts need to be assessed to define reusing strategies that minimize these influences properly. In this study, the effect of reusing cycles on the physical/chemical properties of Ti6Al4V powder produced by plasma atomization and on the mechanical/microstructural properties of printed material was examined. The investigations showed that the powder reusing reduced the number of satellites and the porosity and induced grain coarsening. Moreover, an increase in oxygen content was found after several reusing cycles, resulting in an increase in the hardness of the printed material. The critical defect size was found to increase with reusing cycles, but no significant differences were observed in the fatigue behaviour.