The Influence of Fused Mullite Mineralizer on Mechanical Properties of Ceramic Shell

In order to ensure enough high-temperature strength of the ceramic shell for the investment casting of superalloys, the calcined mullite was added to ceramic shell slurry as the mineralizer. Mullite can be prepared by calcining or fusing. Compared with calcined mullite, fused mullite is purer and more consistent. Thus, in this study, fused mullite was added into ceramic shell slurry instead of calcined mullite to improve the mechanical properties of ceramic shell. It was suggested as the content of fused mullite in ceramic shell slurry increased from 3 to 15 wt%, the high-temperature strength of ceramic shell went up but the high-temperature gravity deformation went down. The high-temperature strength of ceramic shell with 9 wt% fused mullite was 9.33 MPa, which was 89.6% higher than that of ceramic shell with 9 wt% calcined mullite. Meanwhile, the high-temperature gravity deformation of ceramic shell with 9 wt% fused mullite was 0.25%, which was 90.5% lower than that of ceramic shell with 9 wt% calcined mullite. Compared with calcined mullite, fused mullite could promote the generation of secondary mullite phases as the mineralizer.