Constant-load delayed fracture test of atmospherically corroded high strength steels

• Published in: Applied surface science Vol. 257; no. 19; pp. 8275 - 8281
• Main Authors: Akiyama, Eiji, Matsukado, Katsuhiro, Li, Songjie, Tsuzaki, Kaneaki
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.07.2011; Elsevier
• Subjects: Atmospheric corrosion; Certification testing; Circumferences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Delayed fracture; Exact sciences and technology; Fracture mechanics; High strength steel; High strength steels; Humidity; Hydrogen embrittlement; Hydrogen permeation; Load tests; Outdoor; Physics; Delayed fracture; Hydrogen embrittlement; High strength steel; Atmospheric corrosion; Corrosion; High-strength steels
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.03.037

► Constant load test of corroded specimen is useful for evaluating delayed fracture. ► Delayed fracture is controlled by diffusible hydrogen concentration. ► Hydrogen entry is enhanced with progress of atmospheric corrosion. Constant load tests of circumferentially notched round bar specimens of high strength steels after cyclic corrosion test and outdoor exposure have been performed to demonstrate that delayed fracture occurs when the hydrogen content from the environment, H E, exceeds the critical hydrogen content for delayed fracture, H C. During the constant load tests the humidity around the specimen was increased in stepwise manner to increase hydrogen entry. After fracture the specimen was kept at the humidity long enough to homogenize hydrogen in the specimen and to obtain more quantitative hydrogen content by thermal desorption analysis. H E of the fractured specimens was higher than H C, and H E of the specimens not fractured was lower than H C. This result confirms that the balance between H C and H E determines the occurrence of delayed fracture and that hydrogen-content-based evaluation of susceptibility to delayed fracture is reasonable. To certify the increase of H E with increase in humidity, electrochemical hydrogen permeation test was carried out. The hydrogen permeation current density was increased especially at 98%RH. Enhancement of hydrogen entry with increase in CCT number was also shown by the test.