Improvement and application of Y2O3 directional solidification crucible

In order to satisfy the drastic temperature change and high chemical activity in directional solidification of Nb–Si based alloys, Y2O3 crucible is demanded to possess high thermal shock resistance and erosion resistance. This paper improved the sintering degree and density of Y2O3 crucible by optimizing the sintering temperature and time, and its practical application performance was investigated. Y2O3 grains gathered with the increase of sintering temperature and time, and the contact area enlarged, resulting in the open pores being changed into closed pores. The higher density caused the improvement of erosion resistance of Y2O3 crucibles. However, excessive density weakened the thermal shock resistance. Considering high-temperature strength, erosion resistance, thermal shock resistance and costs, optimum sintering temperature and time of Y2O3 directional solidification crucible were 1800 °C and 120 min, respectively, and the porosity was 20%. Improved Y2O3 crucible has been successfully applied to directional solidification of Nb–Si based alloys, and significantly reduced the oxygen contamination. Slight interaction occurred between Hf and Y2O3, but no obvious dissolution, penetration or erosion was found, showing good erosion resistance and thermal shock resistance.