Aptness of the swarf substrate for the additive manufacturing application

Abstract

A novel swarf substrate is proposed for the additive manufacturing process. It was prepared by compressing waste metal chips obtained from the conventional machining processes into a flat plate or any desired shape. It could be disintegrated after the deposition, ensuring ease of part removal. Fused metal chips on the bottom layer require minimal post-processing. A fibre laser and two other arc-based heat sources were used to demonstrate the swarf substrate viability for additive manufacturing. Low alloy steel (ER70S-6) and Inconel 625 were used in this study. Melt pool penetration in swarf substrate was observed to be unique and typically formed a tree root structure after solidification. This structure provides strength for holding the further layers upright. The working parameters were optimised for uniform and continuous deposition. Material integrity was confirmed by hardness study comparison with similar parts deposited on the conventional solid substrate. The dilution of swarf material (typically mild steel) was observed to be limited within 2–3 mm layer height, as confirmed by the Energy-dispersive x-ray spectroscopy. The cooling rate was found to be decreasing with layer height and saturated after few initial layers of the deposition similar to the conventional solid substrate. Excellent formability of the swarf substrate allowed to utilise it for unique applications such as deposition of curved features and support structure. The presented work demonstrates additive manufacturing of parts using such geometrical features, including coil spring and alloy wheel. • A novel approach to recycle the swarf as substrate for additive manufacturing. • Successfully performed for three heat sources, i.e. laser beam, MIG and TIG. • A unique tree root structure formed by the swarf/chips to hold the beads. • The substrate facilitates overhang and curved feature deposition. • Material and heat source does not affect the performance of the swarf substrate.