Effects and Degradation Pathways of NaCl-assisted Hot Corrosion of a 2nd Generation Ni-based Superalloy at 900 °C

The effect of adding NaCl to typical hot-corrosion deposits on a 2nd -generation Ni-based superalloy was studied. Mechanistic understanding was aided by conducting complementary tests of NaCl deposit on pure Ni. The degradation pathway for Ni deposited with NaCl was inferred by conducting a time study of short-term exposures to involve Ni dissolution, precipitation, and subsequent oxidation instead of the commonly posited active oxidation process. Such a degradation pathway is previously unreported, and it highlights the dynamic interplay of degradation mechanisms. The pathway for PWA 1429 with a NaCl deposit included the same initial Ni dissolution and precipitation pathway, while also including an active oxidation component due to the presence of Cr, Mo, or W additions. The results demonstrate that the consideration of NaCl is important to future Na ₂ SO ₄ testing due to the aggressive nature of NaCl, particularly in the early stages of degradation.