Novel Zirconate Based Moulds for the Investment Casting of Titanium Alloy Melts

Nicole Lippert1, Claudia Legner2, Christina Faßauer3, Ulrich E. Klotz4, Christos G. Aneziris5, Lisa Freitag5, Stefan Schafföner6

1 Institute of Ceramic, Glass and Construction Materials, TU Bergakademie Freiberg, Freiberg/Germany
2 fem Research Institute for Precious Metals and Metals Chemistry, Schwäbisch Gmünd/Germany
3 Institute of Ceramic, Glass and Construction Materials, TU Bergakademie Freiberg, Freiberg/Germany
4 fem Research Institute for Precious Metals and Metals Chemistry, Schwäbisch Gmünd/Germany
5 Institute of Ceramic, Glass and Construction Materials, TU Bergakademie Freiberg, Freiberg/Germany
6 Department of Materials Science and Engineering, Norwegian University of Science and Technology NTNU, Trondheim/Norway

Revision 30.11.2017, 09.12.2017

Volume 10, Issue 2, Pages 74 - 79

Abstract

Investment casting allows the near net shape production of complex cast parts, but the investment casting of high melting and highly reactive titanium alloy melts is very difficult. Calcium zirconate (CaZrO3) is a novel ceramic refractory material, which is particularly stable in a highly reducing atmosphere and in contact with extremely reducing titanium alloy melts such as Ti6Al4V. Besides the refractory, the choice of the binder is equally important because conventional silicate binders significantly impair the corrosion resistance. Although there have been successful attempts to develop CaZrO3 investment casting moulds, silicafree CaZrO3 investment casting moulds using a water-based binder have not yet been reported. For the first time, graded CaZrO3 investment casting moulds using a silica-free water-based binder system were successfully produced [1]. Moreover, the chemical, physical, thermo-mechanical and microstructural properties of the moulds were described. A combination of fine-grained primary coats and coarse-grained secondary coats resulted in a high surface quality as well as sufficient mechanical stability of the moulds. Investment casting of Ti6Al4V led to an exceptionally low hardness increase of the cast part, suggesting that only a slight corrosion reaction took place. Thus, the silica-free CaZrO3 investment casting moulds contributed to an improved investment casting of titanium alloys.

Keywords

investment casting, silica-free moulds, titanium alloy melts

References

[1] Freitag, L.; et al.: Silica-free investment casting moulds based on calcium zirconate. Ceram. Int. 43 (2017) [9] 6807–6814 [2] Kim, S.K.; et al.: Investment casting of titanium alloys with CaO crucible and CaZrO3 mold. In: Lightweight alloys for aerospace application. Hoboken, NJ, USA 2001, 251–260 [3] Frueh, C.; et al.: Attempts to develop a ceramic mould for titanium casting – A review. Int. J. Cast Met. Res. 9 (1996) [4] 233–239 [4] Schafföner, S.; et al.: Corrosion behavior of calcium zirconate in contact with titanium aluminide melts. J. Europ. Ceram. Soc. 35 (2015) [3] 1097–1106 [5] Schafföner, S.; et al: Investigating the corrosion resistance of calcium zirconate in contact with titanium alloy melts. J. Europ. Ceram. Soc. 35 (2015) [1] 259–266 [6] Klotz, U.E.; Heiss T.: Evaluation of crucible and investment materials for lost wax investment casting of Ti and NiTi alloys. Int. J. Cast Met. Res. 27 (2014) [6] 341–348 [7] Frueh, C.; et al.: The effect of silica-containing binders on the titanium/face coat reaction. Metall. and Mater. Trans. B. 28 (1997) [5] 919–926 [8] Schafföner, S.; et al.: Fused calcium zirconate for refractory applications. J. Europ. Ceram. Soc. 33 (2013) [15–16] 3411–3418 [9] Salmang, H.; Scholze, H.: Keramik. Berlin, Heidelberg 2007 (in German)

Copyright

Göller Verlag GmbH