Journal of Welding Science

In Wire and arc additive manufacturing (WAAM) based on Gas metal arc welding (GMAW) is one of the methods of manufacturing metal layer by layer. One of this method's basic steps is predicting the welding geometry created in each welding step. In the current research, an experimental study was conducted in this field considering the effective parameters of welding geometry. For this purpose, three parameters of voltage, welding speed, and wire feeding speed were considered as effective parameters on the welding geometry of the process. The width and height of the weld bead was selected as the answer according to the type and application of the research. The least squares support vector machine was used to model the welding geometry in the process. The results obtained from the regression (R2) of train, test, validation, and total were 0.945, 0.793, 0.894, and 0.881 respectively. The comparison between the experimental data and the model data shows the significance of the proposed model.

In the present study, 316L stainless steel walls were fabricated using the WAAM process under controlled primary parameters including welding current, voltage, torch travel speed, and wire feed rate. The solidification behavior, microstructural evolution, and mechanical performance of the WAAM-produced 316L stainless steel were systematically investigated. Microstructural observations revealed that the final structure consists of a γ austenitic matrix containing approximately 8.5% δ ferrite. Tensile testing demonstrated the simultaneous achievement of high strength and ductility. Specimens extracted perpendicular to the build direction exhibited an ultimate tensile strength of about 569 MPa, a yield strength of 378 MPa, and an elongation of approximately 69%. Mechanical anisotropy was estimated to be around 7.5%, attributed to the directional growth of columnar grains. The enhanced ductility compared to conventional cast steels is associated with the fully austenitic matrix, the controlled amount of δ ferrite, the refined dendritic microstructure, and the localized annealing effect resulting from the deposition of successive layers. Microhardness measurements along the build height indicated a gradual decrease in hardness with increasing distance from the substrate, caused by grain coarsening due to heat accumulation and the lower cooling rates in the upper layers. Overall, the findings demonstrate that the WAAM process is capable of producing 316L stainless steel with a balanced combination of high strength and ductility, provided that solidification behavior and thermal history are properly controlled. These results may serve as a basis for microstructure optimization and anisotropy reduction in industrial additive manufacturing applications.