Effect of cooling media on bead geometry, microstructure, and mechanical properties of wire arc additive manufactured IN718 alloy

Abstract

This work aims to present and explore thermal management techniques for the wire arc additive manufacturing (WAAM) of IN718 components. Excessive heat can be mitigated via air or water cooling. In this study, the material was deposited under four different heat-input conditions with air or water cooling. In air cooling, the layer is deposited in a normal atmospheric air environment, whereas with water cooling, the material is deposited inside a water tank by varying the water level. To validate the air and water cooling thermal management techniques, IN718 single-pass and multilayer linear walls were deposited using the bidirectional gas metal arc welding based WAAM setup under four different heat input conditions. During the deposition of single layers, the temperature profiles were recorded, and the geometric and microstructural features were explored. For multilayer wall structures, the mechanical properties (hardness, tensile strength, and elongation) were determined and assessed using the corresponding microstructural features explored through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) analyses. The microstructure observed through SEM analysis in the building direction was found to be nonhomogenous compared with that in the deposition direction. Moreover, water cooling was found to govern bead characteristics, such as wall width and height. The grain size and anisotropy of the mechanical properties also decreased in the water-cooled case. Hence, water cooling is an economical and efficient method to mitigate excessive heat accumulation in WAAM-deposited IN718.