The directionally solidified single crystal DD4 superalloy was prepared using the spiral grain selector. Microstructure evolution and grain competitive growth of the starter block and spiral part in spiral selector were analyzed. The results indicate that with the increase of the height of the starter block

the primary dendrite spacing is increased and the grain density is decreased significantly

and the texture of <001> is strengthened. The orientation deflection angle of the initial grains is less than 10 ° at the height of the starter block of 20 mm. Finally

about 35 grains with obvious size and good orientation can be entered into the spiral part. Grains located in the inner edge of spiral channel were dominant in the process of spiral selection and were the easiest to be selected. The single crystal screening process was realized at the 1/3 helix height of the spiral part

and the single crystal with the deviation angle of 8.9° was prepared.