Fracture behavior in Charpy impact tests of wire arc additively manufactured (WAAM) carbon steel wall components

Abstract This study aims to clarify the challenges associated with applying conventional fracture evaluation methods to wire arc additive manufactured (WAAM) carbon steel components. Charpy impact tests were conducted on wall components fabricated using four types of carbon steel welding wires (SG2, SG3, ER110, and ELCOR M70) over a wide temperature range. The results revealed that significant scatter in absorbed energy and fracture morphology can occur even at identical test temperatures, particularly for SG2 and ELCOR M70. Fracture surface observations and quantitative analysis of cleavage facet size distributions demonstrated that this variability is significantly influenced by inherent microstructural heterogeneity in WAAM-fabricated materials. In addition, local microstructural variation at the notch root, which is intrinsically included in the Charpy testing method, is reflected in the results. In contrast, SG3 and ER110 exhibited relatively stable fracture behavior with smaller scatter, corresponding to their more homogeneous microstructures. These findings indicate that the scatter observed in Charpy impact test results reflects underlying microstructural heterogeneity, suggesting that careful interpretation of test results is required. Furthermore, detailed fractographic analysis enables the detection of toughness heterogeneity in these materials. This provides a practical basis for interpreting fracture test results in heterogeneous additively manufactured materials.