ABSTRACT
Grain structure and texture evolution in the castings were simulated using a three-dimensional version of the stochastic microstructural model detailed by C. A. Gandin et al. The thermal model described previously was used to calculate the thermal history and the microstructure model was then applied subsequently in a post-processing operation. Single-crystal blading for gas turbine applications is expensive—a figure of £1000 per blade for some applications is not unreasonable—and this is because a significant fraction of the castings which are produced in the foundry exhibit defects which lead to non-conformance and waste. For single-crystal blading, significant causes of scrap are freckling, stray grain formation particularly around re-entrant features and inadequate control of wall thickness, particularly for cooled blades. The fabrication of single-crystal components, commercial practice involves the use of a grain selector to ensure that only a single grain enters the cavity of the casting.
