Stability and corrosion behavior of AlO_<i>x</i> coating on T91 steel and SIMP steel in static liquid Pb-Bi eutectic at 600 ℃

Abstract

Ferritic/martensitic steels, such as T91 steel and SIMP steel, are chosen as the main candidates of structural materials for the Generation IV lead-cooled fast reactors and accelerator driven system. However, the compatibility between container steel and liquid Pb-Bi eutectic (LBE) at high temperature limits their applications. The corrosion of ferritic/martensitic steels is serious in LBE at 600 ℃. In order to avoid corroding the ferritic/martensitic steels in LBE, it is proposed to coat AlO_<i>x</i> (<i>x </i>< 1.5) on the steel surface. The AlO_<i>x</i> coating is conducted on T91 steel and SIMP steel by magnetron sputtering. In this exploratory work, the corrosion results of AlO_<i>x</i> coating steel are compared with the corrosion results of the uncoated steel in LBE with a saturated oxygen concentration at 600 ℃ for 300 h and 700 h. The results show that the AlO_<i>x</i> coating can effectively prevent the iron chromium and oxygen from diffusing, so the oxide scale of the coated steel is thinner than that of the uncoated steel. However, the coating cracks after 700 h corrosion in LBE. Meanwhile, T91 steel and SIMP steel also suffer serious oxidative corrosion, indicating that the coating can protect the substrate from being corroded by 600 ℃ static LBE in a short time. However, the coating cannot keep stable for a long time in LBE at 600 ℃. This may be due to the weak film base bonding force of AlO_<i>x</i> coating prepared under the experimental conditions, or a large number of metal aluminum and structural defects existing in AlO_<i>x</i> coating. It is needed to further study the stability of AlO_<i>x</i> coating in LBE at elevated temperature.