A feasibility study on the circular manufacturing of sustainable metal additive manufacturing powders from machining chips

The holistic vision of the research is to develop a circular hybrid manufacturing framework to achieve 'Net Zero' for additive manufacturing sector by producing sustainable powders from production scrap/machining chips. This paper reports an initial feasibility study results from the foundation stage of the circular hybrid manufacturing framework that centres on generating additive manufacturing powders via solid-state crushing/ball milling of machining chips at room temperature. Here, the viability of the ball milling process to produce additive powders from three readily available chip materials is evaluated, viz. a low carbon steel (AISI 1020), and two aluminium alloy chips (AA6082-T6 and AA5083-H111). The ball-milled powders were characterised in terms of their morphology, size distribution, flowability and phase analysis. The morphology/size distributions were found to be influenced by the chip materials and their length scale. Single-track laser melting of pre-placed AA6082 ball-milled powder particles was subsequently performed to emulate the laser powder bed fusion process. Cross-sectional micrographs demonstrated melting and bonding of the ball-milled particles to the AA6082 substrate. A further feasibility trial was undertaken to fabricate cubes from the ball-milled AA5083 powders via the powder bed fusion process. The microhardness (71-88 HV0.01) and microstructure of the specimens were comparable to rolled AA5083-H111 plates.