Strain energy density-distance criterion for the initiation of stress corrosion cracking of alloy X-750

Conference · Wed May 01 04:00:00 EDT 1996

OSTI ID:226450

Hall, Jr, M M; Symons, D M

A strain energy density-distance criterion was previously developed and used to correlate rising-load K{sub c} initiation data for notched and fatigue precracked specimens of hydrogen precharged Alloy X-750. This criterion, which was developed for hydrogen embrittlement (HE) cracking, is used here to correlate static-load stress corrosion cracking (SCC) initiation times obtained for smooth geometry, notched and fatigue precracked specimens. The onset of SCC crack growth is hypothesized to occur when a critical strain, which is due to environment-enhanced creep, is attained within the specimen interior. For notched and precracked specimens, initiation is shown by analysis to occur at a variable distance from notch and crack tips. The initiation site varies from very near the crack tip, for highly loaded sharp cracks, to a site that is one grain diameter from the notch, for lower loaded, blunt notches. The existence of hydrogen gradients, which are due to strain-induced hydrogen trapping in the strain fields of notch and crack tips, is argued to be controlling the site for initiation of cracking. By considering the sources of the hydrogen, these observations are shown to be consistent with those from the previous HE study, in which the characteristic distance for crack initiation was found to be one grain diameter from the notch tip, independent of notch radius, applied stress intensity factor and hydrogen level.

• Research Organization: Bettis Atomic Power Lab., West Mifflin, PA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC11-93PN38195
• OSTI ID: 226450
• Report Number(s): CONF-9604120--5; CONF-960588--1; ON: DE96009884
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
36 MATERIALS SCIENCE
CHROMIUM ALLOYS
CRACK PROPAGATION
CRACKS
FATIGUE
HYDRAULICS
HYDROGEN EMBRITTLEMENT
IRON ALLOYS
MATERIALS
MATERIALS TESTING
NICKEL ALLOYS
NOTCHES
PIPES
REACTOR COOLING SYSTEMS
STRAINS
STRESS ANALYSIS
STRESS CORROSION
STRESS INTENSITY FACTORS