Corrosion damages of nickel-based alloy G3 in 600 °C H2OCO2H2SH2 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.