LASER BEAM MELTING OF WATER ATOMIZED IRON BASE ALLOY FE-4800 WITH IN-SITU ALLOYING OF CARBON NANOPARTICLES

Additive Manufacturing via Laser Beam Melting (LBM) enables production of complex metallic structures with mechanical properties equal or superior to those of conventionally manufactured samples. The huge advantages offered by the layer by layer manufacturing process come with equally increased production costs, mainly due to low build rates and certain process-specific powder quality requirements. Therefore, powder cost reduction is of high interest in order to further establish the LBM process in serial production. Current part production via LBM is performed based on inert gas atomized powders, partially because of their low oxygen content and their spherical shape. Spherical particles serve for a high flowability which is beneficial for a homogeneous layer deposition during the build. Water atomized powders offer great potential with regard to atomization cost, but their irregular particle shapes and their corresponding low flowability require thorough consideration in advance in order to maintain a stable process. This work investigates the suitability of water atomized Fe-4800 powder for the use in LBM manufacturing process. Both particle morphology and flowing characteristics of the water atomized powder are examined, before layer deposition performance is investigated both exemplarily via camera imaging and on-process during part build with the focus on powder layer homogeneity. The samples produced are inspected with regard to microstructural defects related to inhomogeneous powder layer deposition. In-situ-alloying of carbon black nanoparticles in the range of 20 nm to 100 nm is performed to increase powder flowability and to raise the initially low hardness of the material for a wider industrial application range. The samples produced are subjected to measurements of their chemical composition and microhardness. The research results presented show that water atomized Fe-4800 powder is applicable for the use in LBM process, potentially cutting powder cost by a considerable amount compared to inert gas atomized Fe-4800 powder.