Characterization of an austenitic stainless steel preform deposited by wire arc additive manufacturing

Additive manufacturing (AM) is a fabrication process based on the addition of material by layers and has shown several advantages against other manufacturing processes, such as low cost and possibility of manufacturing parts with complex geometries. However, the additive manufacturing can change the properties of the workpiece due to the strategy of multilayer deposition, which can cause changes in the microstructure of the deposited material. In this sense, this work aimed to evaluate the chemical composition, microstructure, and mechanical and electrochemical behavior of the 316L stainless steel manufactured by wire and arc additive manufacturing (WAAM), comparing it with a sample of the same alloy in the annealed condition, trying to understand how the different layers interfere in the final behavior of the material. The results indicate that the microstructure of the deposited material is different with the presence of ferrite in an austenitic matrix. Two regions whose microstructure had different morphologies were also identified in the WAAM alloy. In the region close to the fusion line between the deposited layers, the austenite grains are smaller, about 5 μm wide, against 10 μm of the grains in the area most to the center of the layers. This microstructural change caused an irregular microhardness profile, with an average of 276 HV, higher than the 190 HV of conventional material. It was also observed that the WAAM process caused a decrease in the yield strength (YS) (23%) and elongation (78%) of the alloy and a slight increase in the value of ultimate tensile strength (UTS) (9%); however, it still meets the minimum requirements for most industrial applications required for the material studied (min. UTS 485 MPa, min. YS 170 MPa, and min. elongation 35 MPa). Moreover, the electrochemical results in simulated seawater solution indicate that the corrosion potential of the deposited sample is like that of the conventional specimen (about 0.24 V), with the potential passivating of the first to be superior to that of the second, respectively, 0.640 V and 0.560 V.