Sensitization characteristics for type 445 ultra-pure ferritic stainless steel with an electrochemical reactivation method

• Published in: Journal of materials research and technology Vol. 30; pp. 5249 - 5257
• Main Authors: Fei, Risheng, Liu, Lele, Zhou, Weitao, Bi, Hongyun, Li, Moucheng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-05-2024; Elsevier
• Subjects: 445 ultra-pure ferritic stainless steel; Double loop electrochemical potentiodynamic reactivation test; Intergranular corrosion; Sensitization; Sensitization; 445 ultra-pure ferritic stainless steel; Double loop electrochemical potentiodynamic reactivation test; Intergranular corrosion
• ISSN: 2238-7854
• DOI: 10.1016/j.jmrt.2024.04.251

The sensitization characteristics of type 445 ultra-pure ferritic stainless steel (FSS) under different aging conditions were investigated by the optimized double loop electrochemical potentiodynamic reactivation (DL-EPR) test and microstructure observation. The solution 2 mol L−1 H2SO4 + 0.01 mol L−1 KSCN +0.5 mol L−1 NaCl and a scan rate of 100 mV min−1 are suitable for the DL-EPR test of 445 FSS. With the change of aging temperature from 500 to 900 °C, the degree of sensitization (DOS) slightly increases at first and then decreases, which reaches a maximum value at about 700 °C. Under the aging condition at 700 °C for 10 min to 2 h, the DOS value gradually increases, but it is less than 3% due to the low intergranular corrosion susceptibility. The aging treatment at 700 °C results in the precipitation of Laves phase and (Nb, Ti)(C, N), but no Cr-carbides. The sensitization may be related to the segregation of Cr atoms around (Nb, Ti)-precipitates at the grain boundaries.