CMT deposition of stainless steel: effects of process parameters on energy demand and microstructure

Sustainable manufacturing is gaining momentum as industries strive to minimize the environmental impact of manufacturing and improve sustainability by maximizing the resource efficiency and reducing waste. Additive manufacturing (AM), as a technology that demands fewer raw materials and produces less waste compared to more traditional manufacturing approaches, could inherently support these goals. Among the different AM processes, wire arc additive manufacturing (WAAM) and cold metal transfer (CMT) have shown promise, particularly in the steel production field, where forging, casting and machining have so far been the predominant processes. In order to achieve an effective transition to sustainable manufacturing practices, it is necessary to fully characterize the CMT process, not only from an energy perspective but also by ensuring a high material utilization efficiency and product quality. In this study, the main process parameters have been varied in the deposition of single beads and multilayer structures made of AWS ER 308L Si, and the results have been analyzed in terms of specific energy consumption, microstructure and microhardness of the as-built structures. Overall, the study concludes that the process parameters primarily control energy consumption and the heat applied to the components, rather than the resulting microstructure, which, instead, is influenced more by thermal cycling resulting from the layer-by-layer deposition process. This suggests that process parameters could be selected with a focus on energy savings without significant adverse effects on material properties.