Additive manufacturing of high-precision calcium zirconate molds for advanced investment casting of steel alloys

• Applicant: Dr.-Ing. Lisa Freitag
• Subject Area: Glass, Ceramics and Derived Composites ; Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 538765456

The goal of this project is to develop high-precision investment casting molds based on calcium zirconate (CaZrO3) by means of direct additive manufacturing instead of the lost-wax process and apply them to investment casting of steel alloys in order to investigate the mold–steel interaction. Due to the excellent corrosion resistance of CaZrO3 against other highly reactive metal melts, additive manufacturing of CaZrO3 will most likely offer high added value for demanding foundry applications in the steel industry and beyond. To achieve the goal, the potential of CaZrO3 to be fabricated via two different additive manufacturing processes – binder jetting and stereolithography – will be evaluated by preliminary development of additive manufacturing feedstock (powder- or suspension-based), pre-selection of printing parameters based on literature and feedstock characterization as well as test printing, thermal treatment and investigation of samples with a simple geometry. In addition, the feasibility of integrating the mechanism of alginate gelation in the feedstock processing will be explored. This proof-of-concept approach will allow for choosing the most suitable technique based on target properties for the planned foundry application. It also represents the important milestone of shaping CaZrO3 by means of additive manufacturing, which has not been reported yet. Investigating both binder jetting and stereolithography allows for risk mitigation and could serve as a starting point for other potential applications, e.g. foundry cores. The most promising additive manufacturing technology will be selected for further comprehensive development and subsequent characterization of CaZrO3 molds by binder jetting or stereolithography. For the comprehensive development, the focus will be not only on process scale-up towards more complex samples, but also on materials and process functionalization. Tailoring the properties of materials could comprise granulation by spray-drying, or addition of magnesium oxide to enhance the thermal shock resistance. The process adjustment will focus on debinding and thermal treatment of complex sample geometries with investment casting molds as target geometry. Finally, the novel printed investment casting mold will be used in investment casting trials with two steel alloys. The cast parts as well as the mold will be analyzed after casting to evaluate the mold–metal interaction of CaZrO3 in contact with steel. Cast parts will be characterized regarding their chemical composition, surface quality and dimensional accuracy in order to assess the suitability of the novel investment casting molds. Post-mortem characterization of the molds will allow for an assessment of the recyclability.

• DFG Programme: WBP Fellowship
• International Connection: Finland
• Host: Professor Dr. Erkki Levänen