Binder-Jet Printing of Fine Stainless Steel Powder with Varied Final Density

Binder jetting is an additive manufacturing process that produces weak porous parts that are strengthened through sintering and/or infiltration. This article reports on two different methods of preparing fine 316 stainless steel powder and their impact on the final sintered density and dimensions relative to direct printing into <22 micron powder. The first method uses agglomerates of fine powder. In the second, nylon 12 powders are mixed with the steel powder as a fugitive space holder to increase porosity. Sintered density and sintering shrinkage of agglomerate material are shown to vary with the density of the spread powder bed. Nevertheless, with added nylon, the shrinkage correlates with the shrinkage of the base steel powder, whereas the density depends on the quantity of the nylon. Thus, it is possible to create varied sintered density with compatible shrinkage levels-a key step toward creating binder-jetting systems with spatially controlled porosity.