| Abstract Scope |
Ni-based superalloys are widely used in high-temperature and corrosive environments due to their excellent corrosion resistance, mechanical strength, and toughness. However, during long-term use, the precipitation of the long-range ordered (LRO) Ni₂Cr phase may occur, which can degrade material properties and lead to failure by stress corrosion cracking. This study investigates the addition of cobalt (Co) as a strategy to suppress LRO formation. Alloys with varying Co content were analyzed: Cr₃₃CoₓNi₆₆₋ₓ (x = 0, 5, 17, and 33), Cr₄₀Ni₆₀, Cr₃₁.₇Co₅Ni₆₃.₃, and Cr₂₇.₇Co₁₇Ni₅₅.₃. These samples underwent aging treatments at 475 °C for up to 500 hours. Characterization techniques included Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and microhardness testing. The results show that, for Co contents above 5 at.%, the Ni₂Cr LRO phase is not detected, even after extended aging, indicating that Co effectively suppresses its formation. Only chemical short-range order (CSRO) is observed under these conditions. |