Design of a new wrought CrCoNi-based medium-entropy superalloy C-264 for high-temperature applications. (1st December 2021)

• Record Type: Journal Article
• Authors: Hunfeld, Julian; Sommer, Hannah; Kiese, Jürgen; Wang, Hongcai; Riyahi khorasgani, Ahmadreza; Li, Tong; Somsen, Christoph; Kostka, Aleksander; Laplanche, Guillaume
• Is Part Of: Materials & design. Volume 211(2021)
• Publication Date: 2021-12-01
• Subjects: CoCrNi -- Nimonic C-263 -- Creep -- Corrosion -- Phase stability; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2021.110174
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: Design of a new wrought CrCoNi-medium-entropy superalloy (C-264 MESA) from C-263. ∼5 at.% Cr and 0.85 at.% Ti + Al were added at the expense of Ni while Ti/Al was decreased. The η phase, which forms in C-263 was suppressed in C-264. Due to its higher γ′-solvus, the C-264 alloy has superior creep resistance. C-264 is slightly more prone to nitridation than C-263 due to its higher N solubility. 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.