MODELING OF GRAIN SELECTION DURING DIRECTIONAL SOLIDIFICATION OF SINGLE CRYSTAL SUPERALLOY TURBINE BLADE CASTINGS

摘要

Single crystal superalloy turbine blades are nowadays widely used as key parts in gas turbine engines. The single crystal turbine blade casting's properties are quite sensitive to the grain orientation determined directly by the grain selection behavior of the grain selector. A mathematical model was proposed for the grain selection during directional solidification of turbine blade casting. Based on heat transfer model during directional withdrawing progress, the competitive grain growth within the starter block and the spiral part were simulated by using cellular automaton method (CA). Validation experiments were carried out, and the measured results were compared quantitatively with the predicted results. It is indicated that the model could be used to reproduce the grain morphology and the competitive grain evolution during solidification, together with the distribution of grain orientation of primary <001> dendrite growth direction, with respect to the longitudinal axis of the turbine blade casting.