Geometric and hardness characterization of additively manufactured copper using bound powder extrusion with thermal sintering

Clean Energy Research Group, Department of Mechanical and Aeronautical Engineering, University of Pretoria, South Africa

^* Corresponding author: bradley.bock@up.ac.za

Abstract

Recent advancements now allow for high thermal conductivity metals such as copper to be additively manufactured and will allow for the applications of the technology to be broadened in the field of heat transfer. In this study, copper samples were additively manufactured using a bound powder extrusion process and then characterised in terms of hardness, porosity, mass, volume shrinkage and surface roughness. It was found that this additively manufactured material has a significantly reduced hardness when compared to pure copper and a porosity of between 32-38%. During the manufacturing process a mass loss of up to 8% and a volume loss of up to 28% was seen compared to the original printed part. The surface roughness (R_a) on the sides of the sample was 14 µm while the tops and bottoms of the sample had a surface roughness 8 µm, both significantly higher than parts produced with traditional machining processes. Designers of heat exchangers that makes use of bound powder extrusion will thus have to compensate for geometry changes between the initial print and final part as well as reduced hardness (and likely strength). Greater porosity and roughness of their parts will also have to be considered, which in some cases like boiling can be an advantage, while in convective heat transfer may be disadvantage.