In the MAESTRO project OBE is developing MIM feedstocks and sintered parts for manufacturing complex hybrid MIM/DMLS (Direct Metal Laser Sintering) products. Recently OBE successfully developed the first batches of a MIM feedstock based on different standard 316L powders. 316L is a popular stainless steel alloy for components with enhanced demand on corrosion resistance in all fields of applications. The newly developed feedstocks exhibit an excellent flow behavior for manufacturing injection molded parts without any filling problems. First sintered parts show good material properties regarding chemical composition, microstructure, density and strength.
For feedstock preparation the raw materials (metal powder, binder polymers, and additives) were homogenized in a heated laboratory kneader and afterwards granulated in a commercial rotor cutter. These feedstock granules (see picture on the left) were then appropriate for the shaping process equivalent to plastic injection molding. The feedstock granules were dosed into an injection molding machine which injects the molten, compressed material into a cavity that is the negative of the desired part (see picture on the right).
These manufactured parts, the so-called green parts, were then debindered and sintered to convert the polymer-metal composite into full metallic material. By this process the green parts shrink about the volume fraction of polymer binders (~16-20% in x-y-plane), as can be seen well in in the picture below. The metallic parts are nearly completely dense (> 96%) and can be after-treated with any finishing processes or directly used in the desired application. In further steps of the MAESTRO project these sintered parts are completed by DMLS to manufacture complex hybrid metal parts.