Effect of Construction Manner of Mould Cluster on Stray Grain Formation in Dummy Blade of DD6 Superalloy

Abstract

A dummy blade of Ni-based single crystal (SX) superalloy was modelled to investigate the stray grain (SG) defect by both experiment and simulation. Three construction manners of mould cluster (CMMC) with 0°, 45° and 90° assembling angle were considered. The experimental results reveal a strong dependence of SG sensitivity upon CMMC. Profuse SGs took place in the case of 0°, but almost no one shown in those of 45° and 90°. The FEM simulation results indicate that SG occurrence is not only determined by critical nucleation undercooling, but also the geometrical characteristic, shape of liquidus isotherm and other three important effects (shadow effect, channel effect and dimension effect). The tendency of SG formation increases with the increase of number of these effects. By means of the combination effect consisting of the above three effects, SG occurrence can be qualitatively predicted and process window is more accurately modified.

Keywords

• single crystal
• stray grains
• numerical simulation
• combination effects
• process window