Initiation of environmentally-assisted cracking in low-alloy steels

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Environmentally-Assisted Cracking (EAC) in low alloy steels is activated by a critical level of sulfide ions at the crack tip, which is produced from dissolution of sulfide inclusions (MnS, FeS, etc.) in the steel following exposure by a growing crack. EAC of concern herein is the increase of fatigue crack growth rate of up to 40 to 100 times the rate in air that occurs at 240--300 C in high temperature LWR or boiler water environments. The initiation of EAC is the onset of the higher fatigue crack growth rates in fully developed cracks already presumed to be present due ... continued below

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22 p.

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Wire, G. L. & Li, Y. Y. June 1996.

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  • Bettis Atomic Power Laboratory
    Publisher Info: Bettis Atomic Power Lab., West Mifflin, PA (United States)
    Place of Publication: West Mifflin, Pennsylvania

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Description

Environmentally-Assisted Cracking (EAC) in low alloy steels is activated by a critical level of sulfide ions at the crack tip, which is produced from dissolution of sulfide inclusions (MnS, FeS, etc.) in the steel following exposure by a growing crack. EAC of concern herein is the increase of fatigue crack growth rate of up to 40 to 100 times the rate in air that occurs at 240--300 C in high temperature LWR or boiler water environments. The initiation of EAC is the onset of the higher fatigue crack growth rates in fully developed cracks already presumed to be present due to fatigue, stress corrosion cracking, or induced by fabrication. Initiation of EAC is induced by a change in loading parameters causing the fatigue crack growth rate to increase from a small multiple (2--4) to 40--100 times the air rate. A steady state theory developed by Combrade, suggests that EAC will initiate only above a critical crack velocity and cease below this same velocity. However, more recent tests show that EAC can persist down to much lower velocities (100 times lower) in low oxygen water at slightly lower temperatures. A special set of experiments on high sulfur plate material demonstrate that EAC will not initiate from surface cracks with low sulfide inventories at low crack tip velocities. Transient diffusion calculations show that a finite crack extension at a high crack tip velocity is necessary to initiate EAC, providing a possible explanation for the lack of high crack growth observations reported in low alloy steels in structural applications involving low oxygen environments.

Physical Description

22 p.

Notes

INIS; OSTI as DE96009894

Source

  • American Society of Mechanical Engineers (ASME) pressure vessels and piping conference, Montreal (Canada), 21-26 Jul 1996

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  • Other: DE96009894
  • Report No.: WAPD-T--3091
  • Report No.: CONF-960706--4
  • Grant Number: AC11-93PN38195
  • Office of Scientific & Technical Information Report Number: 251354
  • Archival Resource Key: ark:/67531/metadc670679

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  • June 1996

Added to The UNT Digital Library

  • June 29, 2015, 9:42 p.m.

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  • Dec. 1, 2015, 3:04 p.m.

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Wire, G. L. & Li, Y. Y. Initiation of environmentally-assisted cracking in low-alloy steels, article, June 1996; West Mifflin, Pennsylvania. (digital.library.unt.edu/ark:/67531/metadc670679/: accessed September 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.