Upcycling of electro discharge machining sludge for metal powder manufacturing–Filtration, washing and separation

Sludges from electro discharge machining were processed to reuse metallic particles. The sludge was characterized before dissolving the dielectric with acetone or isopropanol. Pressure filtration experiments were carried out and filter cake resistances computed. To improve material quality, filter cakes were submitted to displacement washing and dilution washing. All filtrates were collected and investigated. Processed particles were visually investigated by scanning electron microscopy and chemically regarding their carbon and oxygen content. Afterward, dry particles were separated by sieving and sifting, fractions analyzed and the separation characterized. Specific filtration resistances show values of 10 14 m –2 . Isopropanol significantly increased processing times compared to acetone. Filter cake washing led to slight improvements of surface quality of particles. For displacement washing, better results were achieved for acetone with approx. 99.5 % removed impurities. Carbon and oxygen contents were in a good range using acetone. Using isopropanol led to detrimentally increased oxygen contents. Particles were separated into fractions for further applications in additive manufacturing. The sifting device applied exhibits a high separation efficiency, with a high sharpness parameter. Several parameter sets were developed for separating particle sizes and powder mixtures. Thermal treatment removed carbon contaminations and oxygen layers on particle surfaces. This work provides a flow scheme for processing oily metallic sludges to obtain a secondary raw material powder. • Erosion sludges successfully upcycled and metallic particles extracted • Regression of cake filtration by non-linear parameter estimation • Filtration and washing properties determined with acetone as suitable solvent • Carbon and oxygen values subsequently reduced by processing • Particle fractions provided for additive manufacturing