Effect of Growth Orientation on the Standard Heat Treatment Microstructure of Nickel-Based Single-Crystal Superalloy DD6

TL;DR

This study examines how the growth orientation of a nickel-based superalloy affects its microstructure after heat treatment.

Contribution

The novelty lies in revealing how growth orientation deviations influence microstructural features like eutectic content and γ′ phase characteristics.

Findings

As growth orientation deviates from <001>, residual eutectic area fraction decreases.

The average size and volume of pores and γ′ phase increase with orientation deviation.

γ′ phase cubicity decreases and size uniformity in dendrite cores reduces with orientation deviation.

Abstract

Using the seeding method, nickel-based single-crystal superalloy DD6 specimens with different growth orientations were prepared in a liquid metal cooling (LMC) directional solidification furnace. Subsequent standard heat treatment was carried out, and the influence of growth orientation on the microstructure of the (001) crystal plane of the alloy after heat treatment was investigated. Results show that with the increase in growth orientation deviation angle from the <001> orientation, the area fraction of residual eutectic content is reduced, the average size and volume of pore and γ′ strengthening phase increase, and the cubicity of the γ′ strengthening phase decreases. The growth orientation does not significantly affect the morphology of residual eutectic content or the morphology of the strengthening phase of the γ′ in the dendrite cores and interdendrite regions. However, the size uniformity of the γ′ strengthening phase in dendrite cores and the width of the γ matrix channels decrease as the growth orientation deviation angle increases.

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