A new strategy for metal additive manufacturing using an economical water-atomized iron powder for laser powder bed fusion

Abstract

We develop a pre-alloyed water-atomized (WA) iron powder for laser powder bed fusion (LPBF)-based 3D printers; such a powder has never been used for 3D printing. The powder features low levels of nano-sized Cu-Ni-Mo; these alloying elements are placed into the concavities of the iron powder. When these powders were used for LPBF printing, the processing window for the volumetric energy density ranged from 93 to 130 J/mm3. However, careful control of laser power (150 – 225 W) and scan speed (500 – 900 mm/s) was essential. In terms of production, a maximum relative density of 99.67% was achieved upon application of an energy density of 108 J/mm3 (175 W, 700 mm/s). An average hardness of 217.1 ± 4.7 HV was obtained, exhibiting stable standard deviations and confirming excellent mechanical homogeneity. Energy-dispersive X-ray spectroscopy mapping revealed excellent chemical homogeneity; this translated to good mechanical homogeneity because of the uniform mixing of the nano-sized alloying elements. The printed tensile bars were stable and of a relatively high aspect ratio. Tensile strength measurements revealed that samples prepared using the partially pre-alloyed iron powder were better than those fabricated from simple raw WA iron powder; the former samples exhibited an ultimate tensile strength (UTS) of 460.91 MPa with elongation of 6.98% and the latter a UTS of 197.15 MPa with elongation of 0.45%. Therefore, the pre-alloyed WA iron powder developed in this study can successfully be used in LPBF and presents a more cost-effective alternative to traditional gas atomized iron powders.