From food enrichment to additive manufacturing: process-structure-property relationships of Atomet 195 SP water-atomized pure iron powder fabricated via laser powder bed fusion

Pure iron is a promising candidate for biodegradable temporary orthopedic implants due to its biocompatibility, favorable mechanical strength, and non-toxic degradation products. Atomet 195 SP is a high-purity water-atomized iron powder commercially produced for food enrichment, pharmaceutical, and other non-structural applications that has never been evaluated for laser powder bed fusion (L-PBF). This study presents the first investigation of its processability by L-PBF, systematically establishing process–structure–property relationships across a volumetric energy density (Ev) range of 34.09 to 120.00 J/mm³. A Taguchi L16 orthogonal array evaluated scanning speed, hatch spacing, and laser spot size. Scanning speed was identified as the dominant control factor for porosity (63.49% contribution, p = 0.007) and surface roughness (57.76% contribution, p = 0.003), with hatch spacing playing a significant secondary role; spot size was statistically insignificant. A processing window of 66 to 100 J/mm³ yielded near-full densification, with a minimum porosity of 0.06% at Ev = 85.71 J/mm³—notably higher than the 47 to 55 J/mm³ optimum reported for Atomet FeAM on the same machine, confirming that parameter transfer between water-atomized powder grades is not reliable. EBSD analysis revealed a fine ferritic microstructure (grain sizes of 4.0 to 5.3 µm) with no detectable secondary phases. Vickers hardness averaged 153 ± 8 HV, a near two-fold increase over conventionally manufactured pure iron, and was insensitive to individual process parameters. Tensile strengths ranged from 431.7 to 508.1 MPa (UTS) and 396.6 to 466.2 MPa (YS), with a pronounced yield point phenomenon at high energy densities that progressively attenuated with decreasing energy input. Two specimens fabricated with different parameter combinations at the same nominal Ev exhibited subtle differences in grain size and mechanical response, reinforcing the limitation of energy density as a sole process descriptor. These results demonstrate that this low-cost, food-grade powder can be successfully processed by L-PBF with mechanical properties comparable to gas-atomized iron feedstocks, supporting its viability for biodegradable implant development.