Effects of cold work on the corrosion behavior of Alloy 800H exposed to aerated supercritical water

Revealing the corrosion mechanism of materials in supercritical water (SCW) is a key issue for the development of a supercritical water reactor (SCWR). Considering cold work is inevitable in the construction of nuclear reactors and its effect on the corrosion behavior of materials in SCW is still unclear, the corrosion behavior of solution-annealed (as-received) and 30% cold-worked Alloy 800H were studied at 600 degrees C in aerated SCW for 1500 h. The microstructure of the oxide scale was studied by a variety of characterization techniques. The results indicate that cold work increases the corrosion rate of the materials, promotes selective oxidation and internal oxidation, and this was attributed to the high diffusion rate of different ions along "short-circuit paths". The oxide scale composition and structure of the cold worked material, which is subdivided to Fe3O4/NixFe3-xO4/NixFeyCr3-x-yO4/Cr2O3/NiO/ FexCr2-xO4 + pure Ni multi-layer structure, are much more complicated than the as-received material after 1500 h exposure. Combined with the thermo-dynamic equilibrium calculation, the oxidation processes of the as-received and cold-worked materials were analyzed to reveal the effect of cold work on the corrosion behavior of Alloy 800H. (C) 2021 Published by Elsevier B.V.