The interface morphologies single crystal superalloys CMSX-2 has been studied over a range of cooling rate with large variations in withdrawal speed in directional solidification. The superfine cellular structure was obtained under both high thermal gradient up to 1000K/cm and fast withdrawal rate up to 1mm/sec. The high rate directional solidification results in reduction in primary and secondary dendrite arm spacing, refinement of lambda' phase, reduced microsegregation. of alloying elements and smaller size of lambda-lambda' eutectics.