Dendrite morphology and evolution mechanism of nickel-based single crystal superalloys grown along the and orientations

Abstract

Nickel-based single crystal superalloys oriented along the <001> and <011> lattice directions were produced by a bottom seeding technique in an attempt to understand the evolution mechanism of the dendrite grown along different orientations in the present study. The changes in primary dendrite arm spacing for single crystal with different orientations are also discussed. It was found that the dendrite morphologies of single crystal superalloy grown along <011> were different from that of <001>. Firstly, the dendrites showed the irregular cruciforms and array in rows in a transverse section. Secondly, no typical primary dendrites were observed but the dendrite morphologies appeared like the letter “V” or “W” in a longitudinal section. The primary dendrite arms grew along the <001> orientation from the bottom of the sample in the <001> orientation. However, in the <011> orientation, the single crystal developed by continuous side-branching along the [001] and [010] orientations. The primary dendrite arm spacing was as the function of the deviation angle ϕ. It indicates that with the increase in the deviation angle ϕ, the primary dendrite arm spacing first increased, and then decreased.