Process parameter windows and their effect on achieved bead geometry and dilution using laser directed energy deposition wire method and 1100 M high strength steel

Laser directed energy deposition wire (L-DED-wire) is an additive manufacturing method in which focused thermal energy of the laser beam and simultaneous wire material feeding is used to form 3-dimensional structures layer-by-layer. The chosen build strategy for these structures largely depends on the resulting material bead geometry, which is in turn influenced by key processing parameters such as laser power, travel speed, and wire feed speed. The resulting bead dimensions can be utilized to predict suitable hatch distance and layer height for build strategy design. The deposition stability assessment is often critical to avoid potential external geometrical defects during processing, e.g. non-fused wire material or excessive melting of the material caused by improper parameter configurations. This study investigates the single-track bead geometry and its dependence on utilized processing parameters, while providing guidelines on deposition stability limits with L-DED-wire method and off-axial 1100M-class metal cored wire material feed. Experimental part of the study is carried out with three different travel speeds, and varied laser power and wire feed rates to determine suitable process parameter windows. The resulting bead width and height dimensions along with surface roughness are analysed with 3D profilometer measurements, while macrograph imaging is performed for machined cross-sections to assess the resulting material dilution and internal defects.