Synergistic sintering and surface coating design for high-temperature wettability and interfacial reaction control of Al2O3-SiO2 ceramics in DD6 superalloy melting

To improve the melt purity of DD6 single-crystal superalloy and mitigate interfacial reactions with Al₂O₃-SiO₂ ceramics during casting, an anti-erosion enhancement strategy that combines sintering parameter optimization with surface coating modification is proposed. By systematically tailoring the sintering temperature and impregnation-coating process, Al₂O₃-SiO₂ ceramics with both superior mechanical properties and refined surface quality were fabricated. On this basis, the high-temperature wetting behavior and interfacial reaction mechanisms between ceramics with different surface conditions and DD6 alloy melt were investigated. Results show that sintering at 1260 ℃yields a dense and homogeneous microstructure with a porosity of 30.5% and a fiexural strength of 12.75 MPa, ensuring thermal stability and structural integrity. The introduction of a dense Al₂O₃ surface coating further reduced surface porosity, suppressed melt infiltration, and retarded interfacial reactions. High-temperature melting tests revealed that the erosion layer thickness decreased from 150 to 200 μm for the uncoated ceramics to ~100 μm for the coated one. Wetting measurements showed that the contact angle between the melt and the ceramic surface increased from 126.15° to 129.77° after coating treatment, indicating weakened wettability. Interfacial characterization confirmed the formation of HfO₂ as a reaction product, evidencing a reactive wetting mechanism. Overall, the synergistic optimization of sintering parameters and surface densification significantly enhances the high-temperature corrosion resistance and service stability of Al₂O₃-SiO₂ ceramics, offering robust engi-neering support for their application in clean melting of advanced superalloys.