Two step, transient liquid phase sintering (TST-LPS) of binder-jet 3d printed nickel-based superalloys

Principal investigator: Markus Chmielus, Ian Nettleship

University: University of Pittsburgh

Industry partners: ExOne

Additive manufacturing (AM) is leading a dramatic transformation of our current manufacturing landscape towards an all-digital approach from model to final product. While a majority of industrial AM applications for metal are utilizing an energy beam-based AM method to produce parts, these methods produce as-printed parts with large thermal stresses and thermally affected microstructures, and are prone to cracking during the manufacturing process. Binder jet 3D printing on the other hand does not have any of these disadvantages but requires a high temperature heat treatment step for densification after an up-to-100x-faster printing process than energy beam AM methods. During a first study, the teams of Drs. Chmielus and Nettleship found that powder size, sintering temperature and sintering duration have a significant effect on final density. The project team of University of Pittsburgh research groups and ExOne, the pioneering and main binder jet 3D printer manufacturing company with headquarters and main manufacturing facilities in PA, propose to significantly enhance the sintering process by investigating a two-step transient liquid phase sintering process for binder jet printed nickel-based superalloys. By systematically investigating how this two-step sintering process influences density, pore evolution, grain microstructure and strength, hardness and fatigue life, this project might lead to a paradigm change in the use of binder jet printing in manufacturing of metal parts. If full density and optimized microstructures could be reached, the resulting mechanical properties would be equivalent to or better than parts made with traditional manufacturing methods. This will enable ExOne to gain a competitive technological edge over its competitors and secure leadership in this AM method for Pennsylvania. The fellowships for one undergraduate and two graduate students will enable fundamental research that will significantly improve advanced manufacturing and directly engage the students with a local PA company.