Abstract:Some active metal oxides (Al₂O₃, TiO₂, and Cr₂O₃) were selected as dopants to the Al₂O₃-based ceramic shells for investment casting of K417G superalloy. The effects of dopant types and contents (0, 2, 5, and 8 wt.%) on the wettability and interfacial reaction between the alloy and shell were investigated by a sessile-drop experiment. The results show that increasing the Al₂O₃ doping contents (0-8 wt.%) reduces the porosity (21.74%-10.08%) and roughness (3.22-1.34 μm) of the shell surface. The increase in Cr₂O₃ dopant content (2-8 wt.%) further exacerbates the interfacial reaction, leading to an increase in the thickness of the reaction layer (2.6-3.1 μm) and a decrease in the wetting angle (93.9°-91.0°). The addition of Al₂O₃ and TiO₂ dopants leads to the formation of Al₂TiO₅ composite oxides in the reaction products, which effectively inhibits the interfacial reaction. The increase in TiO₂ dopant contents (0-8 wt.%) further promotes the formation of Al₂TiO₅, which decreases the thickness of the interfacial reaction layer (3.9-1.2 μm) and increases the wetting angle (95.0°-103.8°). The introduced dopants enhance the packing density of the shell surface, while simultaneously suppress the diffusion of active metal elements from the alloy matrix to the interface.

Key words: Al₂O₃-based ceramic shell; K417G superalloy; metal oxide dopants; interfacial reaction; wettability