Improving mechanical strength and isotropy for wire-arc additive manufactured 304L stainless steels via controlling arc heat input

Wire arc additive manufacturing (WAAM) has the advantage of fabricating large-scale parts with high deposition rate and low costs. But large heat input of WAAM leads to a larger molten pool during deposition, causing coarse grains of formed parts, which tend to have poor mechanical properties of the formed parts. In this study, for reducing heat input, the hot-wire method was adopted to assist WAAM in fabricating 304L austenitic stainless steel (304L SS). Four thin walled square 304L SS components were fabricated by wire arc additive manufacturing with different hot-wire currents. It is found that with the increase of hot-wire current, the arc heat input was reduced obviously. When the hot-wire current is 100 A, the arc heat input was reduced by 70% compared to without hot wire. With the arc heat input reduced, the temperature gradient of the molten pool was decreased, which refines the grains and makes the columnar grains gradually equiaxed, and reduces the anisotropy. The components manufactured in this work have high strength plasticity which the tensile strength up to 720 MPa in a transverse direction with the elongation at 51%.