Researchers analyse nickel-aluminium-bronze ‘chip-powders’ for Directed Energy Deposition feedstock
May 7, 2025
German researchers from the Fraunhofer Institute for Production Systems and Design Technology IPK, Berlin; Mecklenburger Metallguss GmbH, Waren; and Technische Universität Berlin have published a paper in Additive Manufacturing focused on the processability, microstructure and mechanical properties of nickel-aluminium-bronze (NAB) grinding chips – a by-product of ship propeller manufacturing – when recycled as feedstock for Directed Energy Deposition (DED) Additive Manufacturing. The paper compared the ‘chip-powders’ produced by the comminution processes ball milling and impact whirl milling, as well as re-melting via ultrasonic atomisation.
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The researchers characterise the materials via digital image analysis, standardised flowability tests, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy and compare the feedstock to conventional gas atomised powder. The specimens deposited via Directed Energy Deposition are then analysed for density, hardness and microstructure; tensile properties for vertical and horizontal build-up directions are also compared.
At elevated mill rotation speeds, the comminution with impact whirl milling produced rounded particles, favourable flow properties and particle size distribution, making them suitable for Additive Manufacturing. The microstructure exhibited characteristic martensitic phases due to the high cooling rates of the AM process. The presence of ceramic inclusions was observed in both the powder and on the tensile fracture surfaces, partly impairing the mechanical properties. However, specimens in the vertical build-up direction (Z) showed competitive tensile results, with 775 MPa in tensile strength, 455 MPa in yield strength and 12.6% elongation at break.
The researchers noted that these findings indicate that recycling of machining chips into Additive Manufacturing feedstock can be a viable option for reducing material costs and environmental impact.
‘Recycling nickel aluminium bronze grinding chips to feedstock for Directed Energy Deposition via impact whirl milling: Investigation on processability, microstructure and mechanical properties’ is available here.
