Corrosion fatigue crack growth in clad low-alloy steel. Part 2, Water flow rate effects in high sulfur plate steel

Conference · Mon Apr 01 04:00:00 EST 1996

OSTI ID:230548

James, L A; Lee, H B; Wire, G L; Novak, S R ^[1]; Cullen, W H ^[2]

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1. Bettis Atomic Power Lab., West Mifflin, PA (United States)
2. Materials Engineering Associates, Inc., Lanham, MD (United States)

Corrosion fatigue crack propagation tests were conducted on a high- sulfur ASTM A302-B plate steel overlaid with weld-deposited Alloy EN82H cladding. The specimens featured semi-elliptical surface cracks penetrating approximately 6.3 mm of cladding into the underlying steel. The initial crack sizes were relatively large with surface lengths of 22.8--27.3 mm, and depths of 10.5--14.1 mm. The experiments were initiated in a quasi-stagnant low-oxygen (O{sub 2} < 10 ppb) aqueous environment at 243{degrees}C, under loading conditions ({Delta}K, R, cyclic frequency) conducive to environmentally-assisted cracking (EAC) under quasi-stagnant conditions. Following fatigue testing under quasi-stagnant conditions where EAC was observed, the specimens were then fatigue tested under conditions where active water flow of either 1.7 m/sec. or 4.7 m/sec. was applied parallel to the crack. Earlier experiments on unclad surface-cracked specimens of the same steel exhibited EAC under quasi- stagnant conditions, but water flow rates at 1.7 m/sec. and 5.0 m/sec. parallel to the crack mitigated EAC. In the present experiments on clad specimens, water flow at approximately the same as the lower of these velocities did not mitigate EAC, and a free stream velocity approximately the same as the higher of these velocities resulted in sluggish mitigation of EAC. The lack of robust EAC mitigation was attributed to the greater crack surface roughness in the cladding interfering with flow induced within the crack cavity. An analysis employing the computational fluid dynamics code, FIDAP, confirmed that frictional forces associated with the cladding crack surface roughness reduced the interaction between the free stream and the crack cavity.

• Research Organization: Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC11-93PN38195
• OSTI ID: 230548
• Report Number(s): WAPD-T--3096; CONF-9604120--1-Pt.2; ON: DE96008905
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
36 MATERIALS SCIENCE
CORROSION
CRACK PROPAGATION
CRACKS
FATIGUE
FLOW RATE
FLUID MECHANICS
LOW ALLOY STEELS
REACTOR COMPONENTS
REACTOR MATERIALS
SULFUR ADDITIONS
TEMPERATURE DEPENDENCE
WATER