Titanium investment casting is extremely challenging due to the high reactivity of titanium melts. Current crucibles and investment materials are reduced by liquid titanium, resulting in a contamination of the melt and a deterioration of material properties. The paper describes the development of a new shell mold system and crucibles based on calcium zirconate ceramic. Tilt casting and centrifugal casting trials were run in different commercial casting machines on typical-sized jewelry trees. The results using the new ceramic material were compared to commercial shell molds and crucibles that work with a yttria front coat. The role of process parameters (casting conditions, flask temperature, etc.) was studied in detail for titanium grades 2 and 5 and other high-melting, highly reactive alloys. Investigation of the samples by metallography and SEM shows limited reaction with the ceramic and very limited surface hardening. Therefore, the new crucible/shell mold system appears promising for industrial application.

Author: Dr. Ulrich Klotz