Metal additive manufacturing (AM) has been evolving in response to industrial and social challenges. However, new materials are hindered in these technologies due to the complexity of direct additive manufacturing technologies, particularly selective laser melting (SLM). Stainless steel (SS) 316L, due to its very low carbon content, has been used as a standard powder in SLM, highlighting the role of alloying elements present in steels. However, reliable research on the chemical impact of carbon content in steel alloys has been rarely conducted, despite being the most prevalent element in steel. Considering the temperatures involved in the SLM process, the laser–powder interaction can lead to a significant carbon decrease, whatever the processing atmosphere. In the present study, four stainless steels with increasing carbon content—AISI 316L, 630 (17-4PH), 420 and 440C—were processed under the same SLM parameters. In addition to roughness and surface topography, the relationship with the microstructure (including grain size and orientation), defects and mechanical properties (hardness and tensile strength) were established, highlighting the role of carbon. It was shown that the production by SLM of stainless steels with similar packing densities and different carbon contents does not oblige the changing of processing parameters. Moreover, alterations in material response in stainless steels produced under the same volumetric energy density mainly result from microstructural evolution during the process.
A cermet grade with TiCN as major phase and 15wt.% Co/Ni as the binder and secondary carbides WC, Mo2C and NbC was selected for indirect additive manufacturing (Material Extrusion). These powder constituents were the primary material of feedstocks to produce filaments for the indirect AM process - Material Extrusion (MEX). The filaments result from the extrusion of a feedstock previously optimized (CPVC= critical powder volume concentration) and selection of polymeric binder and additive. Concerning the cermet powder particles, 4Ss (particle size, particle size distribution, particle shape, and particle structure) and the quality of the organic binder/additives through the feedstock and filament behaviour were evaluated, in what concerns "printability" and sinterability. Cermet 3D-objects were successfully printed by MEX and sintered. No significant deformation was measured after debinding and sintering, and no undesired phases were detected in the microstructures of the 3D-object.
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