Suppression of anisotropy by wire and arc additive manufacturing with finishing process

Abstract

Additive manufacturing (AM) is attracting more and more interests due to its high material utilization and great flexibility in product design. WAAM is characterized by its ability to manage various metallic materials and high deposition speed. However, its shape accuracy is lower than that of its accumulation via other AM processes and finishing is required as a post-process. In addition, accumulations by AM composed of metal have a complicated thermal history owing to repeated melting and rapid solidification. Consequently, dendritic growth occurs in the microstructure of its accumulation using SUS316L austenitic stainless steel. Therefore, compared with equigranular structures, the mechanical properties of stainless steel, such as ductility and yield strength, are anisotropic. Hence, we herein propose a new system that combines wire and arc additive manufacturing (WAAM) and finishing processing systems. In this method, finishing is performed by the rotating tool when the molten metal solidifies. Experiments using the new system are performed to suppress an anisotropic microstructure by the accumulation of WAAM. As a rotary tool, a cutting tool and a friction stir burnishing (FSB) tool are used. Microstructure observation and X-ray diffraction analysis are performed to evaluate the anisotropy of the accumulation. Using the new system, dendritic growth can be suppressed in an accumulation. By applying the abovementioned simultaneous processing system to the outermost layer of WAAM deposition, improvement in fatigue strength via surface modification and simplification of the finishing process are expected.

Keywords

• wire and arc additive manufacturing
• directed energy deposition
• x-ray diffraction analysis
• finishing process
• cutting
• friction stir burnishing