Cryomilled 17-4 Stainless Steel Powder as Feedstock for Additive Manufacturing

Additive manufacturing (AM) powders supplied by the manufacturer are gas atomized and supplied without post treatment. By including a pre-processing treatment prior to AM, the powder can be modified to improve the mechanical properties of the final build via a reduction in internal powder porosity and grain size refinement. A pre-processing treatment could also change how the powder behaves during the AM process. In this study, as-received gas atomized 17-4 SS powder was ball milled in liquid nitrogen (cryomilling) and then used as feedstock for powderbed fusion (PBF) AM. The effect of powder pre-processing treatment on powder flow and morphology and how changes influence the PBF process and subsequent defect formation in finished parts was examined. Finished parts were characterized through microcomputed tomography and optical microscopy, while the effect on material characteristics was examined via x-ray diffraction and electron microscopy.