XPS, SEM, AFM, and Nano-Indentation characterization for powder recycling within additive manufacturing process

Abstract

Abstract Powder recycling and reducing the waste metallic powder is EU’s key provision in waste framework directive (2008/98/EC). The aim of this investigation is to analyse the correlation between the surface and morphology properties of (virgin and recycled) powders and the microstructure and mechanical properties of the 3D printed parts (made of three powders). Two biomedical Tibia implants have been 3D printed from virgin and 3-5 times recycled powders of stainless steel 316L. For this, the surface composition and microstructure of the powders has been characterized and correlated to the nanoindentation measurements carrier out on these implants. X-ray surface spectroscopy (XPS) has been used to analyse the oxidation level on the powder’s surface revealing less than 10% more oxygen on the surface of recycled powders. SEM analysis shows less than 5 μm difference in powder size distribution even though the shape and circularity of the recycled powders seem to be affected under several reusing cycles. The size of the powder particles does not show much difference but satellites and binding between the powders increased in recycled powder. The hardness and effective modulus of the parts from recycled powders are significantly smaller than the virgin-made implants, which could be due to higher porosity present in the recycled powder or due to oxygen increment on recycled powder. The surface roughness (AFM analysis) has slightly increased on part made of recycled powders. However, the overall morphology shows little difference between the two parts.