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Thermodynamic modeling of oxidation of Al–Cr–Ni alloys

“…In the upper layer the formation of NiO in equilibrium with the Ni(Al,Cr) 2 O 4 spinel is possible. This result agrees well with findings of several experimental works [89][90][91][92][93] in which the presence of these phases during oxidation of Ni-based alloys was experimentally confirmed. As in the case of binary alloys, the Al depletion in the surface region of the ternary alloy was observed.…”

Characterization of oxidation mechanisms in a family of polycrystalline chromia-forming nickel-base superalloys

“…Measured Kp values (in units of kg 2 m -4 s -1 ) range from a maximum of 7.5 x10 -12 for the high-Ti alloy ABD-2 (4.1Ti, 0Nb), down to 1.5 x10 -12 for the low-Ti alloy ABD-6 (2.8Ti, 1.2Nb). This range of Kp values is comparable to values obtained between 750°C and 850°C in a variety of other nickel based superalloys [6,7,9,18,[43][44][45].…”

“…The mechanism by which Ti exacerbates oxidation is a matter of ongoing research. Several previous studies into this behaviour have utilized energy-dispersive X-ray spectroscopy (EDX) [5][6][7][8][9]14,17,18] and electron-probe micro-analysis (EPMA) [10,19] to characterize the distribution of elements through oxide layers. Many of these studies have observed dissolution of Ti into chromia scales, combined with the formation of discrete TiO2 particles at the oxide-air and oxide-metal interfaces.…”

High Temperature Oxidation and Corrosion Properties of High Entropy Superalloys

“…From Figure 2a,b, at 900 °C, neither Cr2O3 nor Al2O3 are formed continuously after 5 h. As for the 1100 °C/5 h exposure results, continuous Al2O3 can be observed in HESA-2 (Figure 2d), while thick external (Ni, Co)O, Co, Fe, Ni and Ti-rich oxides, Cr2O3 and discontinuous Al2O3 are present in HESA-1 (Figure 2c). Although both Cr2O3 and Al2O3 can provide surface protection, Al2O3 would possess lower oxygen permeability and be more thermodynamically stable than Cr2O3, while Cr2O3 may gradually transform into the volatile CrO3 beyond 950 °C (2Cr2O3 (s) + 3O2 (g) = 4CrO3 (g)) [26][27][28][29][30]. Hence, the formation of a continuous Al2O3 layer is critical for protection against oxidation at high temperature.…”

“…Hence, the formation of a continuous Al2O3 layer is critical for protection against oxidation at high temperature. [26][27][28][29][30]. Hence, the formation of a continuous Al 2 O 3 layer is critical for protection against oxidation at high temperature.…”