Corrosion Behavior Of Cold-work 800H And 310S Stainless Steel In Supercritical Water

The supercritical water reactor,as one of the generation IV reactor types recommended by the Generation IV International Forum,has higher thermal efficiency and simplified structure.However,the outlet temperature of CSR1000 design proposed by Nuclear Power Institute of China is 500℃.As for the local hot spot,the temperature will be up to 620℃.The candidate fuel cladding material need to resist the super high temperature and corrosive environment.At present,800H and 310S as two kinds of austenitic alloys are the most promising candidate cladding materials.The cold work introduced by the surface ground and polished,forged and cold rolled processes used in the processing and installation of the cladding material will significantly affect the corrosion behavior of 800H and 310S in supercritical water.The corrosion performance of 800H and 310S after different cold work should be studied in view of lacking relevant data.The effects of three surface states of rough grinding,mechanical polishing and vibration polishing on the corrosion behavior of 800H in supercritical water were investigated.The results show that the coupons with ground surface have a 1/20 of weight gain than those vibratory polished.The slip bands of coupons with ground surface accelerates formation of chromium-rich oxide.The coupon with mechanical polished and vibration polished surface shows double-layer oxide film with outer rich in iron and inner rich in chromium.Besides,corrosion behavior of 800H and 310S with different degree of cold work obtained by forged and cold rolled were studied.The results show that the corrosion rate of the material and thickness of inner chromium-rich oxide layer decreases as the degree of cold deformation increases.When degree of cold work up to 80%,single chromium-rich oxide layer formed after exposed.Effect of the environment including temperature,steam pressure and concentration of dissolved oxygen on stress corrosion crack of cold-worked 800H and 310S.The results show that within 450 ℃-550 ℃ the increase of temperature will significantly accelerate the crack growth rate of cold-worked 800H,while the vapor pressure and dissolved oxygen concentration have little effect on the crack growth rate of the material.