The aim of this study was to determine the optimum conditions of the DL EPR test in order to evaluate the highest values of the degree of sensitization (DOS) of a forged austenitic stainless steel type 316L evaluated by the ratio I r / I a or Q r / Q a in %. The criteria of sensitization to the IGC corresponds to I r / I a > 1% and Q r / Q a > 1%. A model using a full factorial design has been established, and the selected factors were the sweep rate ( dE / dt ), sulphuric acid concentration (H 2 SO 4 ), ammonium thiocyanate concentration (NH 4 SCN), and temperature in ° C. A first order model is obtained by using a 2 4 full factorial design. An experimental test carried out using a 2 4 factorial design indicated that all the factors and their interactions have a positive effect on the response I r / I a . Furthermore, the highest value detected of I r / I a was found to be 65.6%. On the other hand, a microstructural study based on an optical microscope and a scanning transmission electron microscope (STEM) has been carried out for annealed and aged samples (550 ° C-80000 h). The profiles of the chromium, nickel, and molybdenum concentration established by X-ray microanalysis in STEM confirm a decrease of the content of these elements leading to the formation of Cr-depleted zones responsible for the sensitization to the IGC.
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