Influence of Drawing Velocity on the Inner Quality of Single-Crystal Superalloy

This study investigates the inner quality including microdefects, orientation deviation and dendrite spacing of DD6 single-crystal superalloy with different drawing velocities. The XRD, SEM, electron probe microanalyzer methods and mechanical properties were used to evaluate the defects and microstructures, related to their evolution mechanism in DD6 superalloy. It was found that the drawing velocity of 80 μm/s can obtain a 4° deviation angle from the 〈001〉 orientation, less microdefects and well tensile properties. With drawing velocity increasing from 30 to 150 μm/s, PDAS decreases from 471 to 359 μm, respectively. Moreover, the shrinkage porosity decreases firstly and then increases due to different feeding conditions. In addition, the segregation of the solute elements increases and promotes the content of γ/γ′ eutectic, which deteriorate the mechanical properties. The research results can provide a basis for the development of high-quality single-crystal blades.