Interaction mechanism between niobium-silicide-based alloy melt and Y₂O₃ refractory crucible in vacuum induction melting process

The Y₂O₃ crucibles were introduced in the study as an alternative to the traditional ceramic ones in vacuum induction melting of multi-component Nb-16Si-22Ti-2AI-2Hf-17Cr (at.%) alloys, to reveal the possible interactions between the alloy melt and the refractory crucible. Multiple melting time lengths and two cooling schemes were designed and used for the experiments. The chemical composition and microstructure of the tested alloy and the melt-crucible interaction were investigated and evaluated. In the experiments, Y₂O₃ crucible displays good physical-chemical compatibility. The results indicate that the increment of O element in the as-cast ingot is 0.03at.%-0.04at.% (72-97 ppm) and the increment of Y element is very insignificant. The key features of the alloy melt interacting with Y₂O₃ ceramics are analyzed and concluded in the paper. As a result of the dissolution reaction xY₂O₃ (in molten alloy) + (1-x)HfO₂ (impurity) → Hf_1-xY_2xO_2-x, a continuous double-layer solid film consisted of HfO₂solid solution (~2 μm) and pure HfO₂ (~5 μm) is formed on the surface of the test ingot after cooled down in the crucible. The experimental results show that the Y₂O₃ crucible is applicable to the vacuum induction melting of Nb-Si based alloys.