Effects of spiral geometries on grain selection during casting of single crystal superalloys

Abstract

Grain texture evolution in starter block during single crystal (SX) casting with a grain selector had been investigated. Several spiral grain selectors with different spiral geometries were designed to investigate the effects of spiral geometries on grain selection in spiral passage. The results indicated that the percentage of grains with a deviation angle of <10° from the axial orientation increased simultaneously with distance from the chill plate. When the distance reached 36·1 mm, nearly 90 of the grains’ misorientations were <10°, and the minor grains deviated >12°. As the spiral angle θ and the spiral thickness T decrease, the SX structure occurred at the lower position of the grain selector. In addition, it was concluded that the SX structure cannot be selected when the spiral angle is <15°. Moreover, the effect of spiral geometries on grain selection has also been discussed.