The production of specific metal powders for additive manufacturing (AM) by atomization of metal melts is an energy-intensive and cost-driven process. Therefore, it is indispensable to search for alternatives to provide particulate powders. When postprocessing components by electro discharge machining (EDM), erosion sludges are accumulating. In die-sink EDM, the material gets molten and vaporized by conversion of electrical into thermal energy and congeals in the dielectric fluid (oil). These resulting particles meet key size, shape and flowability requirements similar to AM powders [1].

A commonly available martensitic H11 alloy was machined by a mold constructing company and the resulting sludges were collected. The eroded particles were separated, cleaned and classified into AM-factions to provide a source of secondary AM-powders. Their only difference is located in the high carbon content above the eutectic concentration leading to microstructures containing mostly acicular primary cementite [2]. Nevertheless, eroded particles were successfully used in AM processes and final structures characterized.

A common AM-technique is laser beam directed energy deposition of metal powders (DED-LB/M). This process uses a laser to weld gas guided powder streams layerwise to a substrate material. Narrow distributed and spherical particles with good flowabilities are necessary for successfully deposited beads [3]. Defect-free structures of pure recycled particles could be obtained and were analyzed regarding their dilution ratio, hardness and microstructure. Latter one features pearlite, austenite, martensite and cementite due to mixtures of high carbon particles and low carbon substrate. Hardness values are in the range of up to 960 HV10. Several powder mixtures are tested to reduce the risk of residual stresses and enhance the deposition.

Furthermore, smaller sized particles were utilized in binder jetting metal-AM (BJT-M) due to their high carbon content. BJT-M is a sinter-based AM technique, were a dispensed liquid binding agent forms the desired geometries in the powder bed [4]. Due to the good spreadability of recycled particles, a homogeneous powder layer was created. For now, simple geometries were implemented featuring cubic and cylindrical samples as well as tensile test specimen. At least two different sintering regimes are investigated. The developed microstructures are analyzed and mechanical properties as hardness and tensile strength examined.

[1] Voigt, O. and Peuker, U.A., Metals, 2022. 12(9).

[2] Voigt, O., Wendler, M., Siddique, A., Stöcker, H., Quitzke, C. and Peuker, U.A., Metals and Materials International, 2023.

[3] Ahn, D.-G., International Journal of Precision Engineering and Manufacturing-Green Technology, 2021. 8(2): p. 703-742.

[4] Lores, A., Azurmendi, N., Agote, I. and Zuza, E., Powder Metallurgy, 2019.