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Title:Stress corrosion cracking of austenitic stainless steels
Author(s):Juang, Hsun-Kai
Doctoral Committee Chair(s):Altstetter, Carl J.
Department / Program:Materials Science and Engineering
Discipline:Materials Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Mechanical
Engineering, Metallurgy
Engineering, Materials Science
Abstract:In order to understand the stress corrosion cracking behavior of metastable and stable austenitic stainless steels, constant elongation rate tests (CERT) and sub-critical crack growth (SCG) tests were used to measure the susceptibility and cracking rate. The tests were performed in H$\sb2$SO$\sb4$/NaCl solutions in the pH ranges from 0 to 7 and at temperatures from 25 to 75$\sp\circ$C. The AISI 301 (metastable) and AISI 310S (stable) alloys were used for these tests. In CERT, the 301 alloy showed susceptible to SCC while 310S did not. In SCG tests, SCG behavior was analysed with respect to applied potential zones on the polarization curve, i.e. cathodic, active (zone 1), active/passive (zone 2) and passive/transpassive (zone 3). It was found that hydrogen embrittlement (HE) was the main cracking process in zone 1 and cathodic zone for annealed specimens. For deformed specimens, HE was operative in the cathodic zone, but in zone 1 the behavior was not clearly HE. Film rupture and active path corrosion were found to proceed in zone 3. In zone 2, SCC seemed to proceed by a mixture of models. The HE characteristics in 301 alloy was believed to be related to the rate of accumulation of hydrogen at the crack tip. Since stain-induced $\alpha\sp\prime$ phase was verified on the fracture surface, $\alpha\sp\prime$ was considered to play an important role in the HE process. The fast diffusion rate of hydrogen in $\alpha\sp\prime$ phase and low escape rate of hydrogen in the surrounding $\gamma$ phase were believed to be the cause of HE. At potentials more noble than zone 1, the smaller hydrogen charging rate (HCR) was believed to be the cause of immunity to HE, resulting in predominance of dissolution or active path corrosion (APC). The HE process was found to be strengthened by hydrogen recombination poison (NaAsO$\sb2$) in zone 1 and cathodic zone, although it was a corrosion inhibitor. For 310S alloy, 3-stage SCG behavior was observed in pH $$ 4N. A ductile failure morphology was identified for 310S alloy tested in the above solution. The resistance of 310S to SCC was thought to be related to its extremely rapid repassivation rate and high SFE.
Issue Date:1989
Rights Information:Copyright 1989 Juang, Hsun-Kai
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9010905
OCLC Identifier:(UMI)AAI9010905

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