Towards light-weighting high entropy superalloy while retaining ambient strength-ductility synergy, high temperature strength and oxidation resistance

Abstract

Conventional superalloys offer excellent high-temperature strength (HTS), oxidation resistance, and good room-temperature (RT) tensile ductility, however, at the expense of either increased density or high material costs. Here, we present a lightweight (7.53 g/cc) Ni₃₀Co₃₀Cr₁₅V₁₀Fe₅Al₅Ti_2.5Si_2.5 (at. %) high entropy superalloy (Ni-HESA) that achieves a remarkable strength-ductility synergy at RT (1296 MPa, 40 %), excellent HTS (600 MPa at 800 °C), and isothermal oxidation resistance at 900 °C for 96 h exposure (parabolic oxidation coefficient ∼3.693 × 10^–4 mg²cm^-4s^-1) in its most microstructurally complex state. This microstructural complexity in Ni-HESA arises from the presence of γ′ (L1₂Ni₃(Si, Ti) type) precipitate, annealing twins, and grain size modality within the γ-f.c.c. matrix. These features enhance RT work hardenability through back-stress strengthening while ensuring substantial microstructural stability at elevated temperatures, thereby improving both strength and oxidation resistance. The aforementioned property profile of Ni-HESA positions it as a promising superalloy for high-temperature applications, offering enhanced fuel efficiency.