Effect of laser-wire interaction on bead characteristics at non-planar orientations during off-axis directed energy deposition

In the laser-wire directed energy deposition (LWDED) process, the laser-wire interaction (LWI) length directly influences wire melting and the deposition of a uniform layer. However, the effect of LWI length on bead morphology has not been studied due to the lack of a reliable method to calculate LWI length for off-axis wire feed systems. In this work, an analytical model is introduced to predict LWI length at non-planar orientations. The model development considers laser beam diameter, wire thickness, wire feed angles, and substrate tilt angles. It discusses the centre and trailing wire positions on the substrate. Single-bead-on-plate experiments were performed to present the effect of LWI length at non-planar orientations on bead geometry. The experimental findings reveal that the variations in substrate angles and wire feed angles influence bead width, height, and peak shift. The deposited bead geometry was investigated to demonstrate the effect of LWI and laser spot size. This work contributed to investigating the bead geometry at non-planar orientations for the off-axis wire-fed robotic LWDED process. At non-planar orientation, the predicted maximum LWI length was 1.07 mm at a 15° substrate angle and 10° wire feed angle. The melt pool depths were 336 µm, 261 µm, 290 µm, and 183 µm, respectively, with the corresponding laser energy densities of 29 J/mm³, 22 J/mm³, 25 J/mm³, and 16 J/mm³. These findings aid in deciding substrate positions and orientations in additive manufacturing (AM) of thin-walled overhang tubular parts and repair of conformal parts.