The water-atomized ATOMET 28, 1001, 4701, and 4801 powders, manufactured by
Rio Tinto Metal Powders, were used for additive manufacturing by a laser engineered net
shaping (LENS) technique. Their overall morphology was globular and rounded with a size
distribution from about 20 to 200 μm. Only the ATOMET 28 powder was characterized by a strong
inhomogeneity of particle size and irregular polyhedral shape of powder particles with sharp edges.
The powders were pre-sieved to a size distribution from 40 to 150 μm before LENS processing.
One particular sample—LENS-fabricated from the ATOMET 28 powder—was characterized by
the largest cross-sectional (2D) porosity of 4.2% and bulk porosity of 3.9%, the latter determined by
microtomography measurements. In contrast, the cross-sectional porosities of bulk, solid, nearly cubic
LENS-fabricated samples from the other ATOMET powders exhibited very low porosities within
the range 0.03–0.1%. Unexpectedly, the solid sample—LENS-fabricated from the reference, a purely
spherical Fe 99.8 powder—exhibited a porosity of 1.1%, the second largest after that of the pre-sieved,
nonspherical ATOMET 28 powder. Vibrations incorporated mechanically into the LENS powder
feeding system substantially improved the flow rate vs. feeding rate dependence, making it
completely linear with an excellent coefficient of fit, R2 = 0.99. In comparison, the reference powder
Fe 99.8 always exhibited a linear dependence of the powder flow rate vs. feeding rate, regardless
of vibrations.
Keywords: additive manufacturing; LENS technique; globular powder; water atomization