Electrochemical study of intercritically annealed Fe-0.18C-7Mn-4Al steel. (March 2023)

• Record Type: Journal Article
• Authors: Mohapatra, Sudipta; Palai, Debajyoti; Satpathy, Bangmaya; Das, Siddhartha; Das, Karabi
• Is Part Of: Materials today communications. Volume 34(2023)
• Publication Date: 2023-03
• Subjects: Medium manganese steel -- Intercritical annealing -- Corrosion -- Microstructure; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2022.105282
• Languages: English
• ISSNs: 2352-4928

Abstract

Abstract: The present study reports the electrochemical behavior of intercritically annealed (700, 750 and 800 ºC for 60 min) Fe-0.18 C-7Mn-4Al (wt%) steel. The intercritically annealed samples are exposed to a splash and static corrosion environment. The scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron back-scattered diffraction (EBSD) studies reveal the presence of coarse elongated ferrite (EF), reverted austenite (RA) island, fine blocky-shaped intercritical ferrite (IF) and lath martensite in the annealed microstructure. During intercritical annealing, the partitioning of manganese occurs from ferrite to austenite. A large variation of manganese concentration (6.6–9.4wt%) is observed between reverted austenite and elongated ferrite in the sample annealed at 700 ºC. X-ray photoelectron spectroscopy (XPS) and XRD analyses reveal the formation of corrosion products Fe, Fe(OH)2 and Fe3 O4 after the static immersion test. There is a micro-galvanic type of electrochemical corrosion occurring in all the samples where ferrite acts as the cathode and RA as the anode. Both electrochemical impedance spectra (EIS) and potentiodynamic polarization analyses suggest the higher corrosion resistance of the sample annealed at 800 ºC as compared to other annealed samples. For the sample annealed at 800 ºC, the diameter of the capacitance arc, as well as the charge transfer resistance (RCT ) value, are the highest, indicating that the protection ability of corrosion products is strong and the metal dissolution reaction is weak at 800 ºC. Graphical Abstract: ga1 Highlights: Selective dissolution of austenite is responsible for micro-galvanic corrosion. Electrochemical behavior is influenced by intercritical annealing temperature. Annealing at 800 ᵒC results in better resistance to corrosion due to higher RCT.