Investigation on the material extrusion additive manufacturing of unalloyed magnetic steel

Purpose Material extrusion additive manufacturing of feedstocks highly loaded with metal powders (MEX-M) is an emerging method for producing fully metallic components. This study aims to investigate the feasibility of using filament-based MEX-M to fabricate soft ferromagnetic parts and characterizes their magnetic properties. Design/methodology/approach Toroidal specimens were produced by MEX-M using a commercial PLA-based 81 Wt.% Fe filament and a desktop printer. Air thermal debinding was screened by varying heating rate and crucible configuration, and assessed by mass loss and cross-sectional analysis. Using the best cycle, parts were sintered at three temperatures under low vacuum; additional specimens underwent continuous debinding and sintering at the intermediate condition in vacuum or Ar. Density, shrinkage and B–H loops were measured before and after post-sinter vacuum annealing. Findings Low-vacuum sintering at 1,350°C yielded the best results: 92% relative density and saturation magnetization BS = 1.15 T, 65% of commercial pure iron. Vacuum annealing increased BS by up to 10% and reduced coercivity by up to 60%. Oxygen shielding, debinding ramps below 40 K/h and sintering at = 1,350°C limited void formation and deformation, yet residual internal voids persisted across all conditions. Originality/value To the best of the authors’ knowledge, this is the first demonstration of fabricating high-density unalloyed magnetic steel components via filament-based MEX-M. The analysis of debinding and sintering parameters contributes to future filament formulation and process optimization to advance the state of the art.