Flow-induced defects during metal injection molding: Role of powder morphology

Owing to the quality issues of highly filled compounds used in metal injection molding, the current research is focused on intercepting flow-induced inhomogeneities in multiphase compounds resulting from the segregation of metal powder particles from (typically) three/four-component polymer binders, resulting in an unacceptable porosity of the final sintered metal parts. A recently developed nondestructive approach for quantifying the extent of these flow-induced defects was employed to study the effect of the size and shape of water- and gas-atomized 17-4PH stainless steel powders on segregation. This method combines scanning electron microscopy/energy dispersive x-ray spectroscopy with an in-house analytical tool. The results show a higher tendency of coarser particles (D50 of 20 μm) for flow-induced defects, while an irregular shape (water-atomized particles) reduces this unwanted phenomenon.