DIFFUSING HYDROGEN EFFECT ON THE OXIDE FILM ON 316L SS IN HIGH TEMPERATURE WATER

摘要

An experimental setup has been designed todetermine the effect of diffusing hydrogen on the oxidefilm on the outer surface of a steam generator tubes incontact with high temperature water. In this modelexperiment 316L stainless steel tubes are used.Hydrogen gas is injected into the inner side of one tubeto simulate the hydrogen from the primary water, theother tube is exposed to air. The outside surfaces ofboth tubes are exposed to high temperature water at290°C. A double-layered oxide film is formed on boththe control 316L tube and the 316L tube subject tohydrogen diffusion. The outer oxide layer on 316L SS ismainly Fe3O4, which also contains mainly larger-sizedNiFe2O4 at the hydrogen-effusion side of the 316L SStube wall. The inner oxide layer on the 316L SS isalways a Cr-rich oxide but, this oxide layer is thickerwhen there is hydrogen effusion. Ni-content in the outeroxide layer on hydrogen-diffusing 316L SS is higherthan that on 316L SS where there is no hydrogeneffusion. Hydrogen diffusing through the tube wall andexiting the outer surface affects the morphologies andchemical compositions of the outer oxide layer and thethickness of the inner oxide layer on 316L SS in hightemperature water.