Effect of Solidification Defects and HAZ Softening on the Anisotropic Mechanical Properties of a Wire Arc Additive-Manufactured Low-Carbon Low-Alloy Steel Part

Wire arc additive manufacturing (WAAM) is a pioneer additive-based technology for fabrication of large-scale engineering components. Despite the many advances in the field of additive manufacturing, formation of solidification defects, including discontinuities and microstructural imperfections, in the fabricated components is still inevitable, regardless of the feedstock material or fabrication process applied. In this study, the effects of solidification defects on the anisotropic mechanical properties of a low-carbon low-alloy steel (ER70S-6) wall produced by WAAM have been investigated. Analysis of the microstructure and mechanical properties of the fabricated part confirmed the formation of various solidification defects, i.e., interpass lack of fusions, localized brittle zones, and grain coarsening in the heat-affected zones, leading to anisotropic behavior in the ductility along the deposition versus building directions of the component. The effect of discontinuities on the anisotropic mechanical properties was minimized through microstructural modifications of the fabricated part using postprinting normalizing heat treatment.