Effects of yttrium on wettability and interactions between molten superalloy and SiO2-based ceramic core

In order to obtain high-quality superalloy castings, the wettability and interactions between superalloy melts with various Y contents and SiO2-based ceramic cores were investigated at 1823 K. The results indicated that the wettability and interface reactions were affected by the content of Y in the alloy. For the alloys with Y content less than 0.011 wt%, no Y-oxide was found at the interface, but HfO2, Al2O3 and ZrO2 phases were formed, and the wetting angle dropped slightly. However, different Y-oxides precipitated at the alloy-ceramic interface for the alloys with Y content more than 0.017 wt%, and the wetting angle dropped sharply. When the content of Y was 0.017 and 0.025 wt%, Al2O3, Y3Al2(AlO4)(3), HfO2 and ZrO2 phases were formed at the interface. When the content of Y was 0.1 wt%, YAlO3, Y3Al5O12, Y4Al2O9, HfO2 and ZrO2 phases were formed. The formation of different reaction products was mainly caused by the change of Y activity (a(y)) in the alloy. The reaction between Y and SiO2 could improve the wettability of the system apparently.