Investigation of the Undercoolability of Ni-Based Alloys Using High Temperature Thermal Analysis

During the single crystal (SX) solidification of turbine blades, grain defects can form in the platform regions which have abruptly varying cross-sections. A high undercoolability of a Ni-based alloy prevents the growth of stray grains in the thermally undercooled platform area. To evaluate the undercoolability of different Ni-based alloys, temperature measurements were conducted using the same thermal conditions in an Al2O3-SiO2 investment casting shell mold system. Furthermore, the results were compared with stray grains in directionally solidified components.