Mechanical testing and microstructural analysis of wire laser beam directed energy deposited steel plates

Wire laser beam directed energy deposition, referred to herein as DED-LB, has emerged as a key technology in additive manufacturing, enabling the efficient and cost-effective production of large-scale components. By utilising a laser beam to melt and fuse metal wire, DED-LB enables precise control over the deposition process, resulting in parts with a consistent and refined surface finish, which is attracting increasing interest from engineers. However, the limited understanding of the mechanical behaviour of DED-LB steels impedes their broader adoption in structural applications. To address this limitation, a comprehensive experimental study into the microstructure and mechanical properties of DED-LB ER70S-6 carbon steel has been conducted and is presented in this paper. The microstructure of the DED-LB material was examined by electron back-scatter diffraction (EBSD), which revealed a nearly isotropic crystallographic texture. The mechanical response was investigated by conducting a total of 33 tensile coupon tests, comprising 17 as-built and 16 machined specimens extracted in various orientations relative to the layer deposition direction from DED-LB steel plates of two nominal thicknesses. The tensile properties were found to be fairly consistent between the as-built and machined coupons, indicating only a limited influence from the surface undulations. Very minor material anisotropy was observed for the examined specimens, in line with the microstructural observations. In general, the examined DED-LB steel exhibited comparable values of Young's modulus, Poisson's ratio, mechanical strength and ductility to conventionally produced normal-strength steels, highlighting the significant potential of DED-LB for use in construction applications. • Surface undulations of as-built coupons captured using 3D laser scanning showed a negligible effect on mechanical response. • Thinner coupons exhibited higher yield strengths, aligned with the finer grain size. • A weak crystallographic texture revealed in single-pass and oscillatory deposition strategy, explaining nearly isotropic mechanical properties. • Predictive material models for hot-rolled and DED-Arc steels assessed for application to DED-LB carbon steel.