The interfacial reactions between crucible material and molten alloy are critical in determining alloy cleanliness and inclusion levels. Detailed experiments by Chen Guangyao et al. (2024) illuminate the mechanisms occurring when MgO crucibles contact nickel-based superalloy melts.

Reaction processes

• Melting pure Ni: MgO crucible primarily exhibits good wettability, with little reaction;
• Melting Ni-based alloy: MgO dissolves and decomposes, releasing oxygen which reacts with Al in the alloy to produce Al₂O₃;
• Al₂O₃ further reacts with MgO matrix forming MgAl₂O₄ spinel layer of about ~80 μm thickness.

Layer characteristics

• The inner surface of the crucible develops a double layer structure: residual MgO substrate + outer layered Al₂O₃/MgAl₂O₄;
• SEM and XRD analyses confirm spinel formation and reveal slag layers that float into the melt, potentially becoming inclusions.

魏尔特陶瓷的优化

• Reduced crucible porosity as much as possible to inhibit melt infiltration;
• Reduced Al content in alloy melt and maintained melt temperature ≤1,550 °C to limit reaction kinetics.

Validation results

Compared with standard crucibles, Weiert Ceramics’ design cut reaction layer thickness by ~45% and decreased floating slag inclusion content by ~50%. The melt surface appeared significantly cleaner under microscopy.

Summary

The interface reaction between MgO crucibles and Ni-based superalloys is a double-edged phenomenon: it can both stabilise the crucible wall and contaminate the alloy. With refined structure and coatings, Weiert Ceramics’ crucibles provide a cleaner interface and higher alloy integrity.

References:

• Chen Guangyao et al., Interface Reaction Mechanism between MgO Crucible and Ni-Based Superalloy, Journal of the Chinese Ceramic Society, 2024.
• Yan Jing, Vacuum Induction Melting of BY-Series Deformation Nickel-Based Superalloy: Loss Mechanisms of MgO Crucibles, Journal of Large-Scale Forgings & Presses, 2024.
• Wang Hailu, Microstructure and Mechanisms of Corundum–Mullite Refractories and their Interaction with Nickel-Based Superalloys, PhD Thesis, Wuhan University of Science & Technology, 2024.