Control of the substrate heating in laser powder directed energy deposition repairing by bi-directional spiral deposition strategy

Recent improvements in the Laser Powder Directed Energy Deposition (LP-DED) process for repair applications shift the focus to the analysis of possible alterations in the substrate, which is subjected to repeated thermal cycling during deposition of the material. In general, thermal loads can be controlled by changing process parameter. In this work, a two-step bi-directional spiral deposition strategy, alternating between deposition from inward to outward and backfill, is analyzed to evaluate the heating of the substrate and the resulting porosity of the added material. The outcomes indicate the potential of this strategy to control heat flow and achieve a more uniform thermal field. Porosity is minimized by optimizing the hatch spacing, and benefits are observed also in terms of top surface roughness.