Effect of Y content on interface reaction and wettability between a nickel-base single crystal superalloy melt and ceramic mould

Abstract

In this paper, the effect of Y content on interface reaction and wettability between a nickel-base single crystal supperalloy melt and ceramic mould were studied by means of sessile drop tests. The microstructural characterization of the alloy-ceramic interface and the elemental compositions of reaction products were performed by scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA), the phases of reaction products were identified by X-ray diffraction (XRD), and the surface analysis of reaction products was carried out by X-ray photoelectron spectroscopy (XPS). The results showed that Al and Hf in the alloy reacted with SiO2 in the ceramic mould when Y content was lower than 0.011 wt%, and the reaction products were Al2O3 and HfO2, with little change in the wetting angle. However, when Y content was higher than 0.017 wt%, Y and Al in the alloy reacted with SiO2 in the ceramic mould, and the wetting angle decreased significantly. 0.017 wt% was the critical concentration of Y content that would cause interface reactions. The reaction products of 0.017 and 0.025 wt% Y alloys were Y3Al2(AlO4)3, the reaction products of 0.1 wt% Y alloy were Y3Al5O12 and Y4Al2O9, and the reaction products of 0.5 and 1.0 wt% Y alloys were double reaction layer composed of Y2O3 and Y3Al5O12. Si generated by the interface reactions could react with O2 in the atmosphere to form SiOx during the cooling of the alloy-ceramic couples.