Corrosion damages of nickel-based alloy G3 in 600 °C H2OCO2H2SH2 steam

Corrosion damage mechanisms of nickel-based alloy G3 at 600 °C with a mixture of H₂O, CO₂, H₂S and H₂ were explored using ultra-high-temperature and high-pressure corrosion experiments, slow strain rate tensile tests and a series of microscopic characterization methods. Results unveil that G3 alloy exhibited a low corrosion rate on average. The corrosion product film consists of two layers – an inner layer of Cr₂O₃ and an outer layer of a mixture of Ni₃S₂ and Cr₂O₃. The material experienced plasticity losses of 49.5 % and 24.3 % after corrosion and aging, respectively. Precipitation of M₂₃C₆ at grain boundary occurred after corrosion and aging, resulting in chromium depletion and intergranular corrosion within weak grain boundary regions, which reduced plasticity of G3 alloy.