Quantitative analysis of withdrawal rate on stray grain formation in the platforms of a Ni-Based single crystal dummy blade

Quantitative analysis of withdrawal rate on stray grain (SG) formation in the platforms of Ni-base single crystal (SX) dummy blades was carried out through experiments and simulations. The results showed that the tendency of SG formation becomes higher with the increase of withdrawal rates from 3 to 12 mm min⁻¹. Considering that SG formation is governed by a competition on the amount of time used for the dendrites branching and the cooling process, the underlying mechanism associated with the influence of withdrawal rate on SG formation was then investigated based on the effect of withdrawal rate on the thermal profile development and the macrostructural evolutions. Finite element simulation indicated that the thermal profile in the platform is wave-shaped, which results in two kinds of SGs formation; one being isolated in small areas in the platform ends, and the other connecting to a large area across the upper and lower edges of the platform.