Special shell mold for solidification of undercooled nickel-based alloy melts

Shell molds composed of SiO2, SiO2–B2O3, SiO2–ZrO2–B2O3, and ZrO2, Al2O3, as well as ZrSiO4, were prepared. Various undercoolings were obtained with pure nickel, Ni–Cu alloy, and the commercial DD3 single crystal superalloy melts in these molds. It was found that all these molds have a good non-catalytic nucleation effect on pure nickel and Ni–Cu alloy melts, whereas this effect is not obvious with respect to DD3 single crystal superalloy. Only in shell mold composed of ZrSiO4, SiO2–ZrO2–B2O3, and ZrO2 can the DD3 single crystal superalloy be undercooled substantially. Based on the investigation of the structure of shell molds and the calculations using classical nucleation theory, it is demonstrated that ZrSiO4, SiO2–ZrO2–B2O3, and ZrO2 shell molds have an ideal non-catalytic nucleation effect on the DD3 single crystal superalloy melt. Large undercooling and rapid solidification of DD3 single crystal superalloy can be achieved in these three shell molds.