Substrate stimulating technique for Ni-based single crystal superalloy preparation during direction solidification
Binqiang Wang, Long Zeng, Mingxu Xia, Neng Ren, Jianguo Li
Abstract
The grain selector method is a prevailing technique in the manufacturing process of Ni-based single crystal superalloy, however, it cannot control the orientation of single crystal within an appropriate scope. In this study, a novel technique named substrate stimulating method was proposed and DD32 Ni-based single crystal superalloy was prepared. The microstructure evolution was characterized by EBSD and OM, and the temperature field and temperature gradient distribution were predicted by the finite volume method. With a substrate height of 18 mm, the proportion of grains with deviation angles less than 12° and 8° account for 100 % and 99 % at the entrance of spiral selector, compared with 80 % and 51 % by grain selector method, which makes significance sense for optimizing the orientation of single crystal casting and improving the yield of single crystal casting. The morphology and the orientation of the substrate stimulated grains, which are mainly determined by temperature gradient and melt undercooling, could be optimized by adjusting the substrate height and melt pouring temperature.