Influence of process parameters and common printing problems on tensile behaviour of DED-Arc

Wire-arc directed energy deposition (DED-Arc), also known as wire arc additive manufacturing (WAAM), brings about new opportunities for construction decarbonisation and automation. Overall, the mechanical behaviour of DED-Arc steel is largely comparable to conventionally produced structural steel; however, the performance under tensile loading has been shown to be more variable and susceptible to printing defects. Therefore, an experimental study has been conducted to offer deeper insights into the tensile behaviour of DED-Arc steel elements, with a particular focus on the influence of the process parameters and the consequences of common printing problems. Two groups of DED-Arc steel members with I-section profiles were examined. The first group was designed with different wall thicknesses ranging from 3.5 to 8 mm, achieved by varying key printing parameters and toolpaths, as well as with passive or active cooling. The second group featured the same process parameters but with common printing problems intentionally introduced, including layer shifts, unstable shielding gas, wire feed issues, inclusions, lack of preheating and inconsistent stick out. The test specimens were laser scanned to examine their dimensional properties and surface texture, and then loaded to fracture under axial tension. The influence of wall thickness, toolpath and cooling method on the strength and ductility was highlighted. The common printing problems were shown to slightly deteriorate the strength but significantly reduce the ductility, with unstable shield gas and wire feed issues being the most detrimental. These findings mark a crucial step towards the safe use of DED-Arc for load-bearing applications in construction. • Tensile testing of DED-Arc I-section members printed using ER90S-D2 steel wire was conducted. • Influence of wall thickness, toolpath, cooling method and printing problem was investigated. • A method to characterise surface roughness of DED-Arc from 3D scan data was proposed. • Tensile members showed lower strengths and earlier loss of stiffness compared with coupons. • Printing problems mainly impaired ductility, with shield gas and wire feed issues being the most detrimental.