Metal oxide-doped Al2O3-based ceramic shells in DZ125 nickel-based superalloy investment casting modulate wettability and interfacial reactions

Reactions at the interface between DZ125 nickel-based superalloys and Al 2 O 3 -based ceramic shells during investment casting adversely affect the surfaces of the resultant castings. Here, the effects of incorporating metal oxide dopants (HfO 2 , Al 2 O 3 , and Cr 2 O 3 ) on the shell surfaces were investigated. The influence of dopant types and content (0–8wt%) on wettability and reactions at the interface was comprehensively analyzed via the sessile drop approach, followed by evaluation of the products and mechanisms. The findings demonstrate that enhancing the dopant amount markedly decreased shell surface porosity and roughness, mitigating molten metal corrosion. At high dopant contents (2wt%–8wt%), the angle of contact between the alloy and the shell improved while the contact area decreased, concurrently reducing the formation of sand sticking defects and reaction products. Thermodynamic analyses reveal the following mechanisms: the HfO 2 dopant enhanced the chemical stability of the shells and effectively suppressed interfacial reactions. Furthermore, the Al 2 O 3 dopant moderately improved shell stability but did not completely suppress displacement reactions between Hf and Al 2 O 3 , and the Cr 2 O 3 dopant increased reactivity yet promoted the formation of a protective HfO 2 layer that curbed further reactions. These findings demonstrate that doping Al 2 O 3 -based ceramic shells with metal oxides effectively regulates alloy-shell interfacial reactions, enhancing alloy surface integrity while maintaining favorable wettability.