Direct recycling of machine chips through a novel solid-state additive manufacturing process

Abstract

Recycling of metal waste for feedstock material in additive manufacturing (AM) is typically carried out through energy extensive melting and solidification processing techniques. However, in austere environments, energy production can be limited and thus melting down scrap into powder through an atomization process is not a viable approach to producing feedstock from reclaimed waste. However, advancements in solid-state material processing has led to a novel additive manufacturing process that uses solid, macroscale structural feed-rods that allow for high deposition rates with wrought-like mechanical properties. This process, additive friction stir deposition (AFS-D), leverages friction between the rotating feed-rod and the substrate (or previous deposition layer) to soften and promote material flow that creates a plasticized and metallurgically bonded material layer. As such, the AFS-D approach is ideally suited to directly process metal waste with minimal material preparation. To illustrate this concept, we demonstrate AM builds with refined microstructure and wrought-like properties made using loose machines chips. The results of this study demonstrate the potential to recycle metal machine chips by feeding them directly into the AFS-D process and produce structurally sound depositions that can be used for Point-of-Need manufacturing within austere environments.