High temperature oxidation of alloy 617, 740, HR6W and Sanicro 25 in supercritical water at 650°C

Abstract

In this study, the oxidation behaviour of alloy 617, alloy 740, alloy HR6W and Sanicro 25 was investigated in SCW and vapour environment at 650°C for 320 h. The weight gain and the thickness of the oxide films of samples after exposure in SCW are higher than that in vapour. Inner oxidation phenomena were observed on alloy HR6W and Sanicro 25, which have higher content of Fe. The structure of the oxide films formed on alloy 617, alloy 740, alloy HR6W and Sanicro 25 after exposure in SCW at 650°C for 320 h is composed by a Fe-rich (mainly hematite) outer layer and a Cr-rich inner layer. The thickness of the outer Fe-rich layer is related with the Fe content in alloy matrix. Oxide films spallation phenomena were found on alloy HR6W after exposure in SCW.

Review on chromium coated zirconium alloy accident tolerant fuel cladding

“…It is known that the electrochemical potential and pH value of the water environment in PWR reactor are about −0.5 V SHE and 7.0, respectively. Obviously, it is indicated that a stable Cr 2 O 3 layer would form under normal operation conditions, which was confirmed by several researches on the corrosion behavior of pure Cr metal [56] and Ni-Cr alloys in sub and supercritical water environment [57][58][59][60].…”