Understanding the effect of nitrogen in austenitic stainless steel on the intergranular stress corrosion crack growth rate in high temperature pure water

• Published in: Acta materialia Vol. 60; no. 2; pp. 610 - 621
• Main Authors: Roychowdhury, S., Kain, V., Neogy, S., Srivastava, D., Dey, G.K., Prasad, R.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2012; Elsevier
• Subjects: Annealing; Applied sciences; Austenitic stainless steels; Corrosion; Corrosion environments; Deformation; Exact sciences and technology; Grain boundaries; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Stainless steel; Strain; Strain hardening; Stress corrosion cracking; Transmission electron microscopy; Twinning; Twinning; Transmission electron microscopy; Stress corrosion cracking; Stainless steel; Strain hardening; Water corrosion; Austenitic stainless steel; Temperature; Propagation velocity; Growth; Mechanical properties; Corrosion rate; High temperature; Nitrogen; Intergranular cracking; Intergranular corrosion; Crack propagation; Austenitic steel
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2011.09.053

Understanding the effect of nitrogen content on the crack growth rate (CGR) due to intergranular stress corrosion cracking (IGSCC) in high temperature (288
°C) pure water, in non-sensitised and strain-hardened stainless steel (SS) type 304 LN was the focus of this study. Non-sensitised SS containing two different levels of nitrogen (0.08 and 0.16
wt.%) in the solution annealed condition was strain-hardened by cross-rolling at 200
°C (warm rolling). It has earlier been reported that SS with a higher nitrogen level in the warm rolled condition has a higher CGR in high temperature pure water. Tensile testing was carried out using both the SS in the warm rolled as well as in the solution annealed condition at 288
°C. Samples were prepared for transmission electron microscopy (TEM) from the warm rolled SS and from the tensile tested (at 288
°C) specimens. TEM studies indicated that twinning and shear band formation were the major modes of deformation due to rolling at 200
°C and these feature were observed to terminate at grain boundaries, leading to regions of higher strain and stresses at grain boundaries. Higher nitrogen SS has higher grain boundary strain and stresses making the grain boundary regions more susceptible to IGSCC, resulting in higher CGR values. At 288
°C dislocation entanglement and cross-slip were the predominant modes of deformation.