Magnetically assisted directed energy deposition

Abstract

Poor powder catchment efficiency, is a limiting factor in the adoption of Directed Energy Deposition for the processing of expensive materials, complex shapes and for the sake of energy efficiency. This study demonstrates a novel approach to improve powder catchment efficiency using a magnetic field to direct ferritic steel powder during deposition. Powder catchment efficiency increased to a value of 56% on a flat plane, compared to 26% under the same conditions without magnetic assistance. The mild steel substrate, being ferromagnetic, permitted greater magnetic manipulation of powder and higher powder catchment, compared to the austenitic stainless steel, which is essentially non-magnetic. It is proposed that the increase in powder catchment comes about by both the increased concentration of powder directly beneath the nozzle when passing over a magnet, as well as pre-loading of powder over the positions of magnets, due to rebounding particles, prior to the laser beam reaching them. Magnetic assistance was also shown to significantly improve catchment efficiency at substrate inclination angles of up to 45°. In addition, evidence of compression of deposited tracks was also seen on mild steel when magnets were used. Magnetic assistance therefore has significant potential as a process augmentation for improving material and energy efficiency in directed energy deposition, with the benefit of being able to be retrofitted to existing setups.