Abstract
A path to lowering the economic barrier associated with the high cost of metal additively manufactured components is to reduce the waste via powder reuse (powder cycled back into the process) and recycling (powder chemically, physically, or thermally processed to recover the original properties) strategies. In electron beam powder bed fusion, there is a possibility of reusing 95–98% of the powder that is not melted. However, there is a lack of systematic studies focusing on quantifying the variation of powder properties induced by number of reuse cycles. This work compares the influence of multiple reuse cycles, as well as powder blends created from reused powder, on various powder characteristics such as the morphology, size distribution, flow properties, packing properties, and chemical composition (oxygen and nitrogen content). It was found that there is an increase in measured response in powder size distribution, tapped density, Hausner ratio, Carr index, basic flow energy, specific energy, dynamic angle of repose, oxygen, and nitrogen content, while the bulk density remained largely unchanged.
Highlights
An 18% and 15%, increase was observed in the Basic flow energy (BFE) and Specific energy (SE) values, respectively, for G3 powder when compared to the G0 powder
This study looked into comparing the influence of multiple reuse cycles, as well as powder blends created from reused powder, through various performance metrics such as morphology, size distribution, basic flow energy, specific energy, bulk density and tap density after 500 taps, Hausner ratio and Carr index, cohesive index, angle of repose, oxygen content, and nitrogen content
Investigation into the effect of plasma-atomized Grade 5 Ti-6Al-4V powder reuse on the powder properties as well as properties of powder blends led to the following conclusions: (1)
Summary
Particle morphology has a considerable influence on the powder bed packing density, and on the final component density, where the more irregular the particles, the lower the final density [3]. In terms of powder morphology, spherical or regular equiaxed particles, are less cohesive and tend to flow freely, arrange and pack more efficiently than irregular or angular particles [5]. As shape deviates from spherical, the interparticle friction increases and detrimentally affects the powder flowability and packing efficiency. Medina [6] emphasizes that powder morphology examination should be performed to identify particle shape, the presence of satellites, foreign particles, or contamination. Most powders for PBF processes are manufactured via atomization. Powders used in the EB-PBF process are typically manufactured via plasma atomization (PA).
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