Powder reuse cycles in electron beam powder bed fusion : Variation of powder characteristics

TL;DR

This study systematically investigates how multiple reuse cycles in electron beam powder bed fusion affect powder properties, revealing changes in size, flow, density, and chemical composition that impact process efficiency and quality.

Contribution

It provides the first comprehensive analysis of property variations in reused powders, including the effects of blending reused powders, aiding in optimizing reuse strategies.

Findings

Powder size distribution increases with reuse cycles.

Flow and packing properties deteriorate over multiple cycles.

Chemical oxygen and nitrogen contents rise with reuse.

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 and specific energy, dynamic angle of repose, oxygen, and nitrogen content, while the bulk density remained largely unchanged.