Role of Ca additive on the effect of phase composition and microstructure of BaZrO3 refractory and its interaction with titanium alloys

In this study, the effect of different Ca additives (Ca(OH)(2), CaO, and nano-CaCO3) on the composition and microstructure of the fused BaZrO3 crucible were investigated, as well as their interaction with Ti2Ni alloy during vacuum induction melting. Results showed that the crucibles had the same phase compositions when the doping amounts of Ca additives were the same. Three kinds of Ca additives provided three different grain sizes of CaO precursors to participate in the solid solution reaction. When the doping amount of the Ca additive was 5.3 wt.%, the ZrO2 phase in the fused BaZrO3 was disappeared, and the CaZrO3 phase was founded. The composition of the crucibles doped with 7.7 wt.% Ca additives only consisted of Ba1-xCaxZrO3 and CaZrO3 phase. The relative densities and erosion resistance of the crucibles were improved effectively with the increase of Ca additive content. Moreover, the crucible doped with 7.7 wt.% nano-CaCO3 additive exhibited the highest density and the thinnest erosion layer. The Ba1-xCaxZrO3 and CaZrO3 phases were dissolved by the alloy melt, according to the interaction analysis. In addition, the crucible doped with nano-CaCO3 additive had a higher content of refractory element concentration in the alloy melts in comparision with the other two kinds of crucibles due to their higher number of pores.