Flowability, shape and structure characterization of recycled particles originating from electro discharge machining of H11 alloy

Abstract

There is a need in metal powder manufacturing to provide alternative supplies because the only production method is the energy– and cost–intensive melt atomization. The aim of this study is focused on recycling of metallic particles originating from electro discharge machining. Extracted particles from accumulating erosion sludges fulfill theoretically specifications of powders regarding particle size and shape. Two fractions were analyzed via laser diffraction, image analysis and electron microscopy and compared to the benchmark H11–alloy. Bulk properties were measured and powders were investigated in a powder shear cell regarding flowability. These properties were combined with measurements of particle surface roughness in an atomic force microscope. Powders were examined by micro–computed tomography to obtain particle–discrete data. Recycled particles fulfill requirements regarding size, shape and defects. Their bulk properties align with the reference, showing improved or worsened flowability at certain stresses. Attached graphite in recycled fractions is acting simultaneously as nano–roughness and flow additive. H11 shows an expected flow behavior, and the coarse fraction the smoothest surface. Results of sphericity values cannot support findings for roughness and flowability. Pores within particles are least present for H11, hence recycled fractions have better pore performance compared to literature.