Investment casting of Cr–Si alloys with liquidus temperatures up to 1900 °C

Abstract

In previous studies, chromium–silicon-based alloys have shown promising material properties for high-temperature applications. For chromium–silicon alloys to be processed on a large scale, primary shaping processes must be adapted to the requirements of these alloys. In this work, binary chromium–silicon alloys are primarily shaped using an investment casting process. Ceramic shell molds made of hafnium oxide stabilized zirconium oxide are developed to withstand the thermal, mechanical and chemical stresses resulting from pouring melts with liquidus temperatures of up to 1900 °C. The layered construction of the shell molds leads to a sufficient thermal shock stability. Energy-dispersive X-ray spectroscopy shows that chemical interactions between the shell mold and the melt do not occur, nor oxides are formed to a detectable extent. Microstructure investigations reveal that casting binary chromium–silicon alloys lead to a coarse grain structure with grain diameters above 300 µm. Strength-increasing precipitations of the intermetallic phase Cr3Si (A15 phase) can be detected from a silicon content of seven-atom percent in the as-cast state.