Y2O3-YxAlyOz复合坩埚抗TiAl基合金熔体侵蚀行为与机理研究

Reducing production cost and improving performance stability are problems urgently need to be solved for the large-scale application of complex thin-walled TiAl based alloy precision castings. Vacuum induction melting (VIM) in refractory crucibles is one of the most effective ways. However, the corrosion of refractory crucibles and the pollutions of alloy melts caused by the interactions between highly reactive TiAl based alloys and crucible refractory limit its development. Using the characteristics of improving Y2O3 sintering properties by Al2O3 additon and the high stability of YxAlyOz formed by sintering Al2O3 and Y2O3, the corrosion behaviors and mechanisms of Y2O3-YxAlyOz composite crucible resistance to TiAl based alloy melts will be studied in this project, and the influence of crucible phase composition and microstructure, alloy composition, melting temperature and time on corrosion resistance will be illustrated. The typical parameters which characterize the levels of corrosion resistance of crucible will be established, and the quantitative relationships between the typical parameters and influence factors will be built up. The phase composition and microstructure of refractory crucibles will be designed and optimized to achieve mature preparation technology, quantitative and lasting corrosion resistance of the crucibles. The study of this project will provide theoretical guidance for controlling the interactions between Y2O3-YxAlyOz composite crucible and TiAl based alloys, meanwhile improving the corrosion resistance of crucibles and the purity of alloy melts.

降低生产成本、提高性能稳定性是TiAl基合金复杂薄壁精密铸件大规模应用亟待解决的问题，耐火材料坩埚真空感应熔炼技术的应用是最有效的途径之一，但高活性TiAl基合金熔体与坩埚耐火材料之间的相互作用引起的坩埚侵蚀及合金熔体污染制约了其发展。本项目拟利用Al2O3对Y2O3助烧及Al2O3和Y2O3焙烧形成高稳定性YxAlyOz的特性，开展Y2O3-YxAlyOz复合坩埚抗TiAl基合金熔体侵蚀行为与机理研究，揭示坩埚的相组成和显微结构、合金成分及熔炼温度和时间等因素对坩埚抗熔体侵蚀行为的影响规律和机理；确定科学表征坩埚抗熔体侵蚀性的典型参量，建立典型参量与各影响因素间的定量关系；设计优化坩埚的相组成和显微结构，实现坩埚制备技术成熟化、抗熔体侵蚀定量化和持久化。项目的实施将为控制Y2O3-YxAlyOz复合坩埚与TiAl基合金的相互作用，提高坩埚的抗熔体侵蚀性和合金熔体纯净度提供理论指导。

耐火材料坩埚真空感应熔炼技术是解决TiAl基合金精密铸件大规模应用问题的最有效途径之一，但高活性TiAl基合金熔体与坩埚耐火材料之间的相互作用引起的坩埚侵蚀及合金熔体污染制约了其发展。本项目利用Al2O3对Y2O3助烧及Al2O3和Y2O3焙烧形成高稳定性YxAlyOz的特性，开展Y2O3-YxAlyOz复合坩埚抗TiAl基合金熔体侵蚀行为与机理研究，揭示了坩埚的相组成和显微结构等因素对坩埚抗熔体侵蚀行为的影响规律和机理；确定科学表征坩埚抗熔体侵蚀性的典型参量，设计优化了坩埚的相组成和显微结构。. 结果表明，纯Y2O3坩埚的化学稳定性最好，采用纯Y2O3坩埚的熔炼实验，合金内部夹杂物的数量及界面层的反应最低。随着坩埚中Al2O3含量的增加，复合坩埚与熔融合金之间的界面反应减弱。当坩埚中Al2O3的含量由10wt%增加到30wt%时，合金-坩埚界面层的厚度由150 µm减至50µm。Al2O3的添加增加了熔融合金对复合坩埚的润湿性。金属与坩埚之间的平衡接触角由 69.3◦减小到64.2◦。. 对于纯Y2O3陶瓷，当显气孔率增加时，TiAl合金熔体在Y2O3陶瓷上的铺展速率降低，合金熔滴的平衡接触角增大，这导致合金侧界面的粘砂层厚度增大，以及合金基体中陶瓷颗粒增加，界面相互作用增强。致密的陶瓷结构可以提高Y2O3陶瓷的抗侵蚀性，提高合金的质量。. 项目的实施将为控制Y2O3-YxAlyOz复合坩埚与TiAl基合金的相互作用，提高坩埚的抗熔体侵蚀性和合金熔体纯净度提供理论指导。