Binder Jetting – Influence of the Processing Atmosphere on Process Robustness and Part Quality of 17-4 PH Stainless Steel

Doctoral thesis, 2025

Optimizing Binder Jetting through Controlled Processing Atmospheres

Binder Jetting (BJT) is a promising 3D printing technology for creating complex metal parts with high productivity and low costs. BJT works like an inkjet printer but uses thin layers of metal powder instead of paper. Instead of ink, a liquid glue (binder) is jetted onto the powder layer. Layers are printed on top of each other, gluing the particles together.

Once printed, the glued part is “hardened” (curing) in an oven, allowing the part to be freed from the surrounding unglued powder. Afterward, the part is placed into a furnace to burn out the binder (debinding) at elevated temperatures and bake the metal powders together (sintering) near the melting temperature.

This research examined how the atmosphere during curing, debinding and sintering affects the BJT process and final part quality. Curing in air causes powder oxidation, which makes reusing unglued powder problematic. Switching to an inert atmosphere solves this as it prevents oxidation.

Debinding and sintering in inert atmospheres leave harmful binder residues in the part, reducing the part quality. Efficient debinding requires reactive molecules like oxygen or hydrogen. While debinding and sintering in hydrogen is effective, the explosiveness makes it unpopular. A safer alternative is debinding in an oxygen-containing atmosphere followed by sintering under an inert gas. Reducing the oxygen content during debinding compared to air balances binder removal and powder oxidation, improving the final part quality.