Metal Additive Manufacturing Conference - MAMC 2020

At the National Institute for Nuclear Physics – Padova Division, the main research of the Development and Innovation on Additive Manufacturing Group is focused on developing new materials for the Laser Powder Bed Fusion (LPBF) technology. One of the major benefits of this technology is the possibility of fabrication of complex geometries and features in only one-step of production. In particular, for the realization of the heat exchangers, this is very convenient for the realization of conformal cooling channels that can improve the performance of the heat transfer capability. In the context of nuclear fusion, this technology could be applied for the manufacturing of the copper acceleration grids of the Neutral Beam Injector. However, obtaining dense copper parts printed via LPBF presents two major problems: the high reflectivity of 1 μm (the wavelength of commonly used laser sources) and the high thermal conductivity of copper that limits the maximum local temperature that can be attained. This lead to the formation of porous parts. Currently, the major solutions for printing pure copper with high density is to use high laser power (>1 kW), use different laser wavelength (green or blue laser) or divert to copper alloys. However, in literature, there is a lack of research on the influence of the powder size distribution on the printability of pure copper. In this work, the influence of the particle size distribution of the powder on the physical and mechanical properties of parts produced via LPBF is studied. Copper powders purchased from three different companies with three different particle size distributions are used in this study. For the manufacturing of the samples, an EOS INT M280 printer with a maximum laser power of 370 W was used and research was carried out to find the optimal process parameters (laser speed, hatching distance, scanning strategy, etc ..) for obtaining dense parts. Subsequently, samples manufactured with the optimal process parameter were analyzed for thermal conductivity and mechanical properties through tensile and surface hardness tests