Corrosion Fatigue Crack Growth in Clad Low-Alloy Steels—Part I: Medium-Sulfur Forging Steel

1997 ◽  
Vol 119 (3) ◽  
pp. 249-254 ◽  
Author(s):  
L. A. James ◽  
T. A. Auten ◽  
T. J. Poskie ◽  
W. H. Cullen
Keyword(s):  
Fatigue Crack ◽  
Corrosion Fatigue ◽  
Compact Tension ◽  
Initial Crack ◽  
Aqueous Environment ◽  
Low Alloy Steels ◽  
Surface Cracks ◽  
Low Oxygen ◽  
Corrosion Fatigue Crack ◽  
Alloy Steels

Corrosion fatigue crack propagation tests were conducted on a medium-sulfur ASTM A508-2 forging 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 30.3–38.3 mm, and depths of 13.1–16.8 mm. The experiments were conducted in a quasi-stagnant low-oxygen (O2 < 10ppb) aqueous environment at 243°C, under loading conditions (ΔK, R, and cyclic frequency) conducive to environmentally assisted cracking (EAC) in higher-sulfur steels under quasi-stagnant conditions. Earlier experiments on unclad compact tension specimens of this heat of steel did not exhibit EAC, and the present experiments on semi-elliptical surface cracks penetrating cladding also did not exhibit EAC.

Corrosion Fatigue Crack Growth in Clad Low-Alloy Steels—Part II: Water Flow Rate Effects in High-Sulfur Plate Steel

1997 ◽  
Vol 119 (3) ◽  
pp. 255-263 ◽  
Author(s):  
L. A. James ◽  
H. B. Lee ◽  
G. L. Wire ◽  
S. R. Novak ◽  
W. H. Cullen
Keyword(s):  
Surface Roughness ◽  
Fatigue Crack ◽  
Water Flow ◽  
Corrosion Fatigue ◽  
Free Stream ◽  
Crack Surface ◽  
Aqueous Environment ◽  
Low Alloy Steels ◽  
Plate Steel ◽  
Corrosion Fatigue Crack

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 (O2 < 10 pph) aqueous environment at 243°C, under loading conditions (ΔK, 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/s or 4.7 m/s 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/s and 5.0 m/s 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.

Corrosion-Fatigue Crack Growth in Age-Hardened Al Alloys: Examples of Failures and Explanations for Fractographic Observations

2014 ◽  
Vol 891-892 ◽  
pp. 248-253 ◽  
Author(s):  
Rohan Byrnes ◽  
Noel Goldsmith ◽  
Mark Knop ◽  
Stan Lynch
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Compact Tension ◽  
Al Alloys ◽  
Corrosion Fatigue Crack ◽  
Crack Tips ◽  
Corrosion Fatigue Crack Growth ◽  
Additional Support

The characteristics of corrosion-fatigue in age-hardened Al alloys, e.g. brittle striations on cleavage-like facets, are described, with reference to two examples of component failure. Mechanisms of corrosion fatigue (and explanations for fracture-surface features) are then reviewed. New observations of corrosion-fatigue crack growth for 7050-T7451 alloy compact-tension specimens tested in aqueous environments using a constant (intermediate) ΔK value but different cycle frequencies are then described and discussed. These observations provide additional support for a hydrogen-embrittlement process involving adsorption-induced dislocation-emission from crack tips.

scholarly journals The Initiation of Environmentally Assisted Cracking in Semi-Elliptical Surface Cracks

1998 ◽  
Vol 120 (2) ◽  
pp. 200-206
Author(s):  
L. A. James
Keyword(s):  
Experimental Test ◽  
Surface Crack ◽  
Compact Tension ◽  
Initial Crack ◽  
Surface Cracks ◽  
Test Results ◽  
Low Oxygen ◽  
Type Specimens ◽  
Environmentally Assisted Cracking ◽  
Access To Water

A Criterion to predict under what conditions EAC would initiate in cracks in a high-sulfur steel in contact with low-oxygen water was recently proposed by Wire and Li (1996). This EAC initiation criterion was developed using transient analyses for the diffusion of sulfides plus experimental test results. The experiments were conducted mainly on compact tension-type specimens with initial crack depths of about 2.54mm. The present paper expands upon the work of Wire and Li by presenting results for significantly deeper initial semi-elliptical surface cracks. In addition, in one specimen, the surface crack penetrated weld-deposited cladding into the high-sulfur steel. The results for the semi-elliptical surface cracks agreed quite well with the EAC initiation criterion, and provide confirmation of the applicability of the criterion to crack configurations with more restricted access to water.

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