Carburization and Stress Profiles Characterized by High-Energy X-ray Diffraction in 316L Austenitic Stainless Steel After Exposure at 500 °C and 600 °C in Carburizing Liquid Sodium


316L austenitic stainless steel was carburized in sodium containing a high-carbon activity at two different temperatures, 500 °C and 600 °C for 1000 h. The carbon profile, carbide mass fraction and residual stress tensor profile were determined using electron probe microanalysis and high-energy X-ray diffraction. The carbon profile and carbides mass fractions were also predicted using a thermodynamic and kinetic modeling tool (DICTRA). At 600 °C, the experimental results and predictions suggested that the carbon absorbed by the sample was mainly trapped to form M23C6 and M7C3 carbides. The residual stress profile in austenite was strongly dependent on the M23C6 precipitation and the induced modification of the substrate chemical composition. At 500 °C, results and predictions suggested that the carbon was mainly dissolved in austenite. The residual stress profile was governed by the formation of expanded austenite at the sample surface.
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