Residual Stress Analysis in the Oxide Scales Formed on 316L Stainless Steel at 700 degrees C under Humid Air

The effects of water vapor on residual stresses in the oxide scales formed on 316L austenitic stainless steel are investigated. Samples were oxidized in thermogravimetric analyzer at 700 degrees C for 6 hours 96 hours with different amounts of water vapor (air, air+0.5%H2O, air+4.0%H2O). Grazing incidence X-ray diffraction (GIXRD) at different incident angles was used to study the phases and residual stresses in the oxide scales. The results demonstrate the formation of an inner chromia (Cr2O3) or chromium and iron solid solution (FexCr2-xO3) layer and an outer hematite (Fe2O3), iron and nickel metallic compound (FeNi3) and spinel layer. With the presence of water vapor, few wustite (FeO) was also detected near the substrate. The residual stresses in the oxide scales are compressive, while the ones in the substrate are mostly tensile. Water vapor influenced not only the composition ratio of oxide scales and the residual stress levels but also the approach of oxide film damage.