Experimental study on mechanical and high cycle fatigue properties of wire arc additively manufactured carbon steels

Wire arc additive manufacturing (WAAM) is a mature metal 3D printing technique with highly-automation, greater design freedom and large-scale printing capabilities. Applications of WAAM in construction have only emerged in recent years and it has been shown that the mechanical properties are significantly affected by printing process parameterization. In this study, an experimental study into the mechanical and high cycle fatigue (HCF) properties of WAAM ER70S-6 and ER110S-G steels was conducted. A total of 10 tensile coupons under static tensile loading and 31 HCF coupons under constant HCF amplitude loading were tested. Mechanical properties of WAAM steels at room temperature were determined and the axial strain distribution on the as-built surface was observed by digital image correlation (DIC). S-N curves of as-built normal-strength and high-strength steels were derived from test data and compared to the fatigue design curves in IIW Recommendations. Based on 3D laser scanning, geometric measurements of WAAM coupons were performed and the effect of local stress concentration on fatigue life was considered. Additionally, fractography of the tested coupons was performed to assess their failure mechanisms. Comparing two types of as-built coupons, the normal-strength WAAM steel provided less geometric variability and exhibited much better ductility compared to high-strength steel. Normal- strength WAAM steel exhibited better high cycle fatigue behavior compared to both former test results and high- strength steel. Severe stress concentration and multiple fracture mechanisms led to inferior HCF properties of ER110S-G steel. This study extends the WAAM fatigue experimental data pool for carbon steel materials and evaluates the effect of deposition strategies on the material properties, demonstrating promising application prospects in structural engineering.