Thermal-shock stable Al2O3 crucible for superalloy smelting through slip casting with particle gradation

Crucible is a key vessel in superalloy smelting, and high-performance crucible is quite important to the development of superalloy. Pointed at the easy cracking and poor thermal-shock stability of Al 2 O 3 crucibles for superalloy smelting, particle gradation was managed in slip casting of Al 2 O 3 crucibles. The ceramic slurry in good dispersion was prepared by optimizing particle gradation, with solid content of 86 wt% and viscosity of lower than 0.5 Pa s. For the crucible with optimized particle gradation, the density was 2.37 g/cm 3 , the linear shrinkage was less than 2%, the porosity was 18.72%, the bending strength was close to 22 MPa and the thermal expansivity was 2.77 × 10 −6 /°C. Strength retention rate was raised to evaluate the thermal shock stability of crucibles, which was up to 73.5% after five-time thermal shock, well meeting the requirements of crucibles for superalloy smelting, and the superior thermal-shock stability was attributed to the uniform network microstructure and low thermal expansivity. The optimal particle gradation in experiments was explained in terms of Dinger-Funk model. This work provides a reference for preparing high-performance Al 2 O 3 crucibles for superalloy smelting with low thermal expansivity as well as excellent thermal-shock stability.