Corrosion Behavior of GH4169 Alloy under Alternating Oxidation at 900 °C and Solution Immersion

In this paper, the corrosion behavior of GH4169 superalloy under alternating oxidation (at 900 °C) and solution immersion (in 3.5% NaCl solution, 30 ± 1 °C) has been studied by SEM, XRD, XPS, and electron probe microanalysis (EPMA). The results show that the alternating environment increases the corrosion rate of GH4169. The reaction of NaCl and Cr₂O₃ generates various volatile and soluble corrosion products, such as Na₂Cr₂O₇, CrCl₃, Cl₂, and Na₂CrO₄, at a high temperature. The destruction of the protective Cr₂O₃ film leads to the increase of defects in the oxide scale, promoting the formation of oxides, such as NiO and Fe₂O₃, and changes the composition and structure of the oxide film. After repeated iterations, the mixed oxides will result in the spalling of the oxide film because they can reduce the fracture toughness of the corrosion scale. Therefore, the corrosion is comprehensively intensified.