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

Shell molds composed of SiO2, SiO2-B2O3, SiO2-ZrO2-B2O3, and ZrO2, Al2O3, a s well as ZrSiO4, were prepared. Various undercoolings were obtained with p ure nickel, Ni-Cu alloy, and the commercial DD3 single crystal superalloy m elts in these molds. It was found that all these molds have a good non-cata lytic nucleation effect on pure nickel and Ni-Cu alloy melts, whereas this effect is not obvious with respect to DD3 single crystal superalloy. Only i n shell mold composed of ZrSiO4, SiO2-ZrO2-B2O3, and ZrO2 can the DD3 singl e crystal superalloy be undercooled substantially. Based on the investigati on of the structure of shell molds and the calculations using classical nuc leation theory, it is demonstrated that ZrSiO4, SiO2-ZrO2-B2O3. and ZrO2 sh ell molds have an ideal non-catalytic nucleation effect on the DD3 single c rystal superalloy melt. Large undercooling and rapid solidification of DD3 single crystal superalloy can be achieved in these three shell molds. (C) 2 001 Elsevier Science B.V. All rights reserved.