Effect of active metal oxide dopants on wettability and interfacial reaction between K417G superalloy and Al2O3-based ceramic shell

Some active metal oxides (Al 2 O 3 , TiO 2 , and Cr 2 O 3 ) were selected as dopants to the Al 2 O 3 -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 Al 2 O 3 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 Cr 2 O 3 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 Al 2 O 3 and TiO 2 dopants leads to the formation of Al 2 TiO 5 composite oxides in the reaction products, which effectively inhibits the interfacial reaction. The increase in TiO 2 dopant contents (0-8 wt.%) further promotes the formation of Al 2 TiO 5 , 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.