**1. Introduction**

The superior creep resistance, high-temperature strength, and corrosion resistance make Nickel-based superalloys the material class of choice for high-performance applications, such as turbine blades of aircraft turbines. The precipitation of an ordered cubic gamma' phase within the disordered cubic gamma phase with a similar lattice constant leads to the combination of exceptional mechanical properties. While also Pt- and Pdbased superalloys exist (the platinum-group-metals possess a similar fcc structure), their higher costs make a broad commercial use still unfavorable. Common uses of Nickelbased superalloys are turbine components for aircraft and land-based turbines for power generation.

Manufacturing of turbine blades is usually performed by complex casting procedures, such as investment casting and directional solidification. That route generally achieves polycrystalline morphologies with equiaxed grains or grains aligned along the length of the blade. Furthermore, for advanced performance, single-crystal turbine blades are

**Citation:** Miti´c, V.; Serpa, C.; Ili´c, I.; Mohr, M.; Fecht, H.-J. Fractal Nature of Advanced Ni-Based Superalloys Solidified on Board the International Space Station. *Remote Sens.* **2021**, *13*, 1724. https://doi.org/10.3390/ rs13091724

Academic Editor: Serdjo Kos

Received: 31 March 2021 Accepted: 23 April 2021 Published: 29 April 2021

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manufactured, using specially designed alloy compositions, such as CMSX-10. Singlecrystalline components exhibit improved performance and lifetime compared with blades of polycrystalline morphology.
