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Design of a new wrought CrCoNi-based medium-entropy superalloy C-264 for high-temperature applications

Hunfeld, J. and Sommer, H. and Kiese, J. and Wang, H. and Riyahi khorasgani, A. and Li, T. and Somsen, C. and Kostka, A. and Laplanche, G.

MATERIALS AND DESIGN
Volume: 211 Pages:
DOI: 10.1016/j.matdes.2021.110174
Published: 2021

Abstract
A new wrought CrCoNi-based medium-entropy superalloy (MESA) was designed by changing the composition of a commercial superalloy of type C-263, which is used for stationary components in gas turbines. ∼5 at.% Cr and 0.85 at.% Ti + Al were added at the expense of Ni while the Ti/Al ratio was decreased. Owing to these modifications, the brittle η phase, which is stable in C-263 below 900 °C is no longer observed in C-264. Besides, the solvus temperature and volume fraction of the γ′ phase in the peak-aged state are larger in C-264 (∼935 °C, 13.5%) compared to C-263 (∼890 °C, 12.8%), resulting in superior tensile and creep properties. The stress and temperature dependencies of the creep rates were described by power-law and Arrhenius relationships. The stress exponents were between 4 and 5, while the apparent activation energies were 550 and 400 kJ/mol for C-264 and C-263, respectively. During creep at 880 °C in air, internal nitridation in both MESAs resulted in the formation of TiN precipitates, with C-264 being slightly more affected due to its higher nitrogen solubility. Due to its superior creep resistance, good malleability and machinability, the C-264 MESA is currently commercially available from VDM Metals International. © 2021 The Authors

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