A process-driven experimental analysis of different wire-fed Directed Energy Deposition processes employing the Laser, Electric Arc and Plasma sources

Among Metal Additive Manufacturing (MAM) technologies, Directed Energy Deposition (DED) enables large-scale printing. Wire-DED has shown significant growth with various processes using different energy sources, yet a comprehensive comparison is lacking. This study investigates three Wire-fed DED technologies: Laser Metal Deposition (LMD), Plasma Transferred Arc (PTA), and Gas Metal Arc (GMA). A creep-resistant AWS-ER90S-B3 steel wire was used as feed material for the deposition of 20-layers wall specimens from each DED technology, evaluating the effect of heat inputs and deposition rates. For each wall, microhardness tests were conducted, followed by microstructural studies and SEM-EDS analysis. The results revealed that, to achieve similar deposition ratio, PTA results in the highest heat input and LMD the lowest. LMD can be used for obtaining finer dimensions, while GMA has the advantage of providing higher deposition rates; finally, PTA allows for a better printing control and exhibits smoother deposits. The hardness results show slightly higher values for processes with higher energy densities with the order: LMD, PTA, GMA, respectively. All the walls exhibited a bainitic/martensitic microstructure; LMD produced a comparatively finer structure than PTA and GMA, which is in line with the hardness results. The EDS analysis showed comparable elemental composition for the samples produced with the three technologies, without any sign of segregation. The study concludes that either of the processes are competitive for DED-AM applications and the choice of the technology depends on the end-user requirements for deposition rate, process stability or geometrical precision.