Selective Electron Beam Melting (SEBM) of Pure Copper – from Process Development to PropertiesTuesday (27.09.2016) 11:15 - 11:30 Part of:
Additive Manufacturing is a layer upon layer technique which allows the manufacturing of complex components that are not producible with conventional manufacturing techniques. It has been shown before, that selective electron beam melting is a feasible method to additively manufacture pure copper from the powder bed despite its absorption characteristics and the high thermal conductivity. Additionally, the required controlled vacuum environment for a stable electron beam also supports high quality fabrication since it avoids oxidation during melting.
We will present the process development for fully dense and crack-free pure copper components. A relatively (for SEBM) low processing temperature of 380°C is needed due to the high sintering tendency of pure copper. Dense melting occurs above 60 J/mm³ volume energy density. Samples were characterized in respect to mechanical, electrical a thermal properties. The hardness is measured with 60.5 ± 7.2 HV0.05 and the tensile test shows a young’s modulus of 97 ± 4.6 GPa, yield strength of 93.7 ± 0.8 N/mm², tensile strength of 222.9 ± 1.5 N/mm² and a fracture strain of 60.4 ± 3.2 %, which are typical values for annealed copper. Even more interesting are the electrical and thermal conductivity. Experiments exhibit that the conductivity are in close correlation with the Wiedemann–Franz law and results at the maximum in an electrical conductivity of 56 MS/m and a thermal conductivity of 400 W/mK. Analyses of samples fabricated from various raw powders with different Phosphorous contents show, that besides pores especially Phosphorous could be identified as main impact factor for reducing the electrical and thermal conductivity. In conclusion, this work presents for the first time the option of additively manufactured dense pure copper components with high electrical and thermal conductivity and how these are affected by both processing parameters and raw material.