Corrosion behavior of three heat‐resistant steels for turbine system in steam at 600°C and 20 MPa

The corrosion behavior of KT5916, 2Cr11Mo, and Co3W3 in high‐temperature and high‐pressure steam at 600°C, and 20 MPa were investigated. The kinetic weight gain curves of KT5916 and Co3W3 nearly followed a parabolic law. Oxide scale exfoliation was found in all steels. The oxide layer structural distribution of the three heat‐resistant steels was Fe3O4 layer and FeCr2O4 layer from the gas side to the substrate side, and the critical criterion for the formation of Fe2O3 oxide was 509.3°C. Under the influence of growth stress, the oxide film of the three heat‐resistant steels experienced a stable oxide layer, coarsening of oxide, pulverization of oxide, and exfoliation of oxide in high‐temperature and high‐pressure steam environments. The corrosion kinetic curves of KT5916, 2Cr11Mo, and Co3W3 steels nearly followed a parabolic law in steam at 600°C, and 20 MPa. A double‐layer oxide film with an outer layer of Fe3O4 and an inner layer of FeCr2O4 was formed on the steel's surface. The corrosion behavior consisted of four stages including the formation of a stable oxide layer, coarsening of oxides, pulverization of oxides, and exfoliation of oxide scales.