ANALYSIS OF INTERNAL POROSITIES AND DENSITY ENHANCEMENT METHODS IN AISI 316L SAMPLES OBTAINED BY BINDER-JETTING

Binder-Jetting is an additive manufacturing process characterized by a layer approach, used to produce prototypes or small production series. Polymeric ink is selectively deposited on a metallic powder bed, then the entire volume is put inside a drying oven. Cross-linking of the polymer takes place: this makes it possible to handle the parts which are now more robust. Afterwards, these “green parts” are placed inside a furnace to undergo a thermal de-binding and a sinter cycle. Surface finish is the limit of this technology: many customers are not satisfied with the obtained results, so the parts require post-processing like sandblasting or polishing. Following the removal of the material allowance, the internal porosities located between every single layer show up on the surface, making the parts not suitable for food contact or aesthetic purposes. This is due to the mechanics of deposition and removal of the binder, in addition to the process being powder-based. This experimental study wants to focus on the porosity distribution (in other words the density gradient) in the Binder-Jetting process, considering AISI 316L stainless steel as material. At the end of this document, some density enhancement methods will be proposed.