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SYSTEM FOR HOT FORGING WIRE AND ARC ADDITIVE MANUFACTURING
EP3990207
The present invention refers to an equipment and method intended to melt metal wire using an electric arc as the heat source, more specifically to a WAAM equipment and its method of operation, based on hot forging between deposited layers. The main objective of the process of the present invention is to take advantage of the viscoplastic deformation behaviour at high temperatures, which allows reducing residual stresses, increasing ductility, eliminating post-heating treatment operations and homogenizing the grain structure. The equipment of the invention comprises: a heat source (6.1) configured to apply heat to a portion of a surface of a workpiece sufficient to melt said portion, the heat source being further configured to move relative to the workpiece; a material delivery means configured to add material (1) to the melted portion; cooling means (13) configured to cool the formed layer to bring at least part of the layer to a solid (crystalline) state, thereby producing a modified workpiece; and a controllable forging treatment tool, actuated by a vibrating actuator (3), configured to hot forging the workpiece so as to plastically deform the part layer.
The presence of recrystallized grains in WAAM parts has obvious advantages: first, it can increase the mechanical strength following the Hall-Petch relationship; then, the existence of these refined grains at the top of the deposited layer provides a higher density of nucleation sites, decreasing the susceptibility for massive grain growth as observed in WAAM deposits. Another potential advantage of deforming the as-deposited layers at high temperature is the possibility to improve waviness and surface roughness, increasing part accuracy and reducing material waste upon subsequent machining processes.