Performance of 9Cr Ferritic-Martensitic Steels in Flowing Lead for 8000 h

The performance of two steels (Grade91, Eurofer97) were investigated after exposure to flowing liquid lead at 480 °C and ~1.6 m/s flow velocity with an average oxygen concentration 1 × 10⁻⁷ wt.% up to 8116 h. The testing of cylindrical specimens was done in the MATerial test Loop (MATLoo), a non-isothermal corrosion loop with active oxygen control system consisting of Bi/Bi₂O₃/YSZ sensors and oxidizing/reducing gas dosing system. The corrosion mode was oxidation, both steels developed characteristic triple layer and no dissolution attack was observed. The oxide growth followed logarithmic kinetics. The Eurofer97 specimens were covered with exfoliating continuous scale, oxidized faster and the material loss was almost linear reaching 38 μm at 8116 h. The Grade91 specimens developed thick oxide scale on 95% of the surface of the samples, the remaining surface was covered with very thin oxide of 40–90 nm with or without internal oxidation zone, and detachment of the outer layer was minimal. Surprisingly, the maximum material loss 17 μm was observed on 4082 h specimen, while 50% of surface of 8116 h specimen remained uncovered with magnetite and material loss was only 14 μm.