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A Treatise on Corrosion Science, Engineering and TechnologyEffect of Metallurgical Variables on the Stress Corrosion Cracking Behavior of AISI-Type 316LN Stainless Steel

A Treatise on Corrosion Science, Engineering and Technology: Effect of Metallurgical Variables on... [Nitrogen-alloyed (0.07wt%) 316 low carbon (L) stainless steel is being used as structural material for high-temperature fast breeder reactor components with a design life of 40 years. However, they are prone to localized corrosion attack. Higher addition of nitrogen can increase the localized corrosion resistance since nitrogen stabilizes the passive film. Hence, the present study was carried out with 0.14 wt% nitrogen containing 316LN stainless steel and compared the localized corrosion resistance with 0.07 wt% nitrogen containing 316LN stainless steel. Nitrogen containing 316LN stainless steel in mill annealed, thermally aged, and deformed condition were evaluated for their localized corrosion resistance. Mechanical properties were evaluated by carrying tensile tests at a strain rate of 10–4/s at room temperature. The results were analyzed for yield strength (YS), ultimate tensile strength (UTS), and ductility (% total elongation). Localized corrosion behavior was evaluated by conducting anodic polarization studies in deaerated acidified 1 M sodium chloride medium. Similarly, stress corrosion cracking studies (SCC) were carried out using constant load tests to determine time to failure. SCC studies were carried out at 70% yield strength of the materials in boiling acidified 5 M NaCl + 0.15 M Na2SO4 solution. Time to failure (tf) was the assessment criteria. Critical pitting potential (Epit) was minimum for thermally aged stainless steel followed by deformed nitrogen containing 316LN stainless steel. Mill annealed stainless steel showed the highest Epit values and a maximum resistance to SCC. Pitting corrosion results corroborated very well with stress corrosion cracking resistance. Cold working reduced the time to failure due to the introduction of metallurgical defects and residual stresses in the material. Thermal aging also deteriorated SCC resistance due to the availability of pre-existing active paths for crack propagation due to the depletion of chromium in regions around the grain boundary where carbide, nitride precipitation had occurred. Cracking initiated in the transgranular mode in all the three metallurgical states as observed in scanning electron microscope.] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

A Treatise on Corrosion Science, Engineering and TechnologyEffect of Metallurgical Variables on the Stress Corrosion Cracking Behavior of AISI-Type 316LN Stainless Steel

Part of the Indian Institute of Metals Series Book Series
Editors: Kamachi Mudali, U.; Subba Rao, Toleti; Ningshen, S.; G. Pillai, Radhakrishna; P. George, Rani; Sridhar, T. M.
Toppo, Anita
Springer Journals — May 5, 2022
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Publisher
Springer Nature Singapore
Copyright
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022
ISBN
978-981-16-9301-4
Pages
99 –112
DOI
10.1007/978-981-16-9302-1_6
Publisher site
See Chapter on Publisher Site

Abstract

[Nitrogen-alloyed (0.07wt%) 316 low carbon (L) stainless steel is being used as structural material for high-temperature fast breeder reactor components with a design life of 40 years. However, they are prone to localized corrosion attack. Higher addition of nitrogen can increase the localized corrosion resistance since nitrogen stabilizes the passive film. Hence, the present study was carried out with 0.14 wt% nitrogen containing 316LN stainless steel and compared the localized corrosion resistance with 0.07 wt% nitrogen containing 316LN stainless steel. Nitrogen containing 316LN stainless steel in mill annealed, thermally aged, and deformed condition were evaluated for their localized corrosion resistance. Mechanical properties were evaluated by carrying tensile tests at a strain rate of 10–4/s at room temperature. The results were analyzed for yield strength (YS), ultimate tensile strength (UTS), and ductility (% total elongation). Localized corrosion behavior was evaluated by conducting anodic polarization studies in deaerated acidified 1 M sodium chloride medium. Similarly, stress corrosion cracking studies (SCC) were carried out using constant load tests to determine time to failure. SCC studies were carried out at 70% yield strength of the materials in boiling acidified 5 M NaCl + 0.15 M Na2SO4 solution. Time to failure (tf) was the assessment criteria. Critical pitting potential (Epit) was minimum for thermally aged stainless steel followed by deformed nitrogen containing 316LN stainless steel. Mill annealed stainless steel showed the highest Epit values and a maximum resistance to SCC. Pitting corrosion results corroborated very well with stress corrosion cracking resistance. Cold working reduced the time to failure due to the introduction of metallurgical defects and residual stresses in the material. Thermal aging also deteriorated SCC resistance due to the availability of pre-existing active paths for crack propagation due to the depletion of chromium in regions around the grain boundary where carbide, nitride precipitation had occurred. Cracking initiated in the transgranular mode in all the three metallurgical states as observed in scanning electron microscope.]

Published: May 5, 2022

Keywords: Pitting corrosion; Nitrogen containing stainless steel; Stress corrosion cracking; 316LN stainless steel

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