Grain boundary oxidation behavior of Ni15Cr alloy in high temperature carbon dioxide

The grain boundary (GB) corrosion behavior of Ni15Cr alloy in 650celcius/1bar CO2 gas was investigated. The oxidation behavior of coherent twin boundary is similar to that of grain matrix due to the immobility of Cr. However, the incoherent twin boundary is prone to preferential intergranular oxidation due to the limited Cr diffusivity and the ingress of oxygen. Likewise, low angle GB is also susceptible to intergranular oxidation because Cr diffusion is not fast enough although it can induce GB migration and result in a protective scale at oxide tip. In contrast, random high angle GB is immune to intergranular oxidation because Cr can diffuse quickly to form a protective scale above GB with the formation of a large GB migration zone. Therefore, the oxidation behavior of GB is closely related to the diffusivity of Cr along GB which is determined by the GB structure.

Automated summary

The grain boundary corrosion behavior of Ni15Cr alloy in 650°C/1bar CO2 gas was investigated. It was found that the oxidation behavior of coherent twin boundary is similar to that of grain matrix, while the incoherent twin boundary is prone to preferential intergranular oxidation. Low angle GB is also susceptible to intergranular oxidation, although it can induce GB migration and result in a protective scale. In contrast, random high angle GB is immune to intergranular oxidation.