Corrosion and Stress Corrosion Cracking of 310 Stainless Steel in Supercritical Water

Abstract

In the present study, the effect of exposure duration on the corrosion and stress corrosion cracking of 310 stainless steel tube in a supercritical water environment was investigated at 500 ^oC in a decreasing dissolved oxygenregime.Oxide films formedthreedistinct layers after exposure to SCW for 2500 hours.On the outer layer, large magnetite crystals were observed which were tiny on the surface after exposed for 500 hours.Inthe middle-oxide layer, the concentrations ofiron, chromium and nickel were close tothose in the substrate. In the inner layer, chromium was enriched while iron was depleted. With increasing exposure duration, the thickness of the oxide layer increased. In the sub-layers of magnetite crystals, some iron-deficient regionswere seen because of the selective outward diffusion of iron.Some micro cracks started to form from those iron-deficient regions.