Thermal and microstructural analysis of intersections manufactured by wire arc additive manufacturing (WAAM)

Wire arc additive manufacturing (WAAM) stands out in manufacturing metallic structures due to its great potential for application in industry for automated production of parts with large dimensions and considerable geometric complexity. Due to the wide presence of ribs and wall crossovers in several mechanical components, this work studied the thermal behavior of the low alloy steel wire AWS ER80S-G in a 10-mm-wide and 90-degree intersection, discovering its influence on the microstructure and hardness of the material compared to a flat wall. Thermal analysis showed that the cooling rate at the intersection is lower than that of a flat wall. However, the evaluation of the cooling curves in a CCT diagram of the steel, later confirmed by a metallographic analysis, indicated that the difference between these two regions was insignificant, as the microstructure was quite similar between them (76% ferrite, 20% pearlite, and 4% retained austenite). On the other hand, there was a significant difference among the layers in the same region, ranging from the morphology of acicular grains at the base and top to equiaxed grains in the intermediate region (ASTM grain size 9). This difference in microstructure was significant for the hardness of the material according to the deposited layer; however, there were few differences between the intersection and the flat wall. Therefore, there are no significant differences between these regions concerning the microstructure or cooling rate, with the variances observed in the hardness being more significant only among the layers deposited.