Stress Corrosion Cracking Study of Several High Strength Steels

Davis, R. A.; Dreyer, G.; Gallaugher, W. C.

doi:10.5006/0010-9312-20.3.93t

Cited by 16 publications

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“…Other tests showed that there were no effects of fall times or hold times at minimum load if the preceding rise time was longer than ~80 s or preceding hold time at maximum load was longer than ~80 s. Discussion. In discussing the differences in crack growth rates for the different waveforms, one needs to bear in mind that (i) the maximum K value is well below the sustained-load SCC threshold K value [14], (ii) there was no effect when rise times were long, and (iii) the comparisons have been made for the same rise time and cycle period such that crack growth promoted by electrochemical reactions/adsorbed hydrogen at the external crack tip during the rise time will be fairly similar, and the time available for hydrogen accumulation in nanovoids ahead of cracks is the same. Thus, some of the differences in the da/dN versus cycle-period plots for the different waveforms probably lie in differences in rates of hydrogen accumulation in nanovoids owing to different stress fields, but another difference between the K max -hold waveform and the others is that it is likely that some crack growth occurs during the K max hold time.…”

Section: Corrosion-fatigue Crack-growth Rates In Steels: Effects Of H...mentioning

confidence: 99%

Effects of Waveform and Cycle Period on Corrosion-Fatigue Crack Growth in Cathodically Protected High-Strength Steels

Knop

Birbilis

Lynch

2014

AMR

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Abstract. The processes involved in corrosion fatigue in general are briefly outlined, followed by a brief review of recent studies on the effects of cycle frequency (rise times) and electrode potential on crack-growth rates at 'intermediate' ∆K levels for cathodically protected high-strength steels. New studies concerning the effects of fall times and hold times at maximum and minimum loads on crack-growth rates (for K max values below the sustained-load SCC threshold) are presented and discussed. Fractographic observations and the data indicate that corrosion-fatigue crack-growth rates in aqueous environments depend on the concentration of hydrogen adsorbed at crack tips and at tips of nanovoids ahead of cracks. Potential-dependent electrochemical reaction rates, crack-tip strain rates, and hydrogen transport to nanovoids are therefore critical parameters. The observations are best explained by an adsorption-induced dislocation-emission (AIDE) mechanism of hydrogen embrittlement. Review of Mechanisms and Some General Aspects of Corrosion FatigueFor many materials, embrittling environments (e.g. aqueous, gaseous hydrogen, liquid metals) can increase rates of fatigue crack growth by up to several orders of magnitude compared with the rate in inert environments, with the degree of embrittlement depending on variables such as ∆K, cycle frequency, and the 'potency' of the environment. In addition, the fracture path and fracturesurface appearance can be markedly different in inert and embrittling environments [1,2]. Fatigue in inert environments generally produces transgranular fractures exhibiting 'ductile' striations whereas intergranular or cleavage-like fractures with 'brittle' striations are observed after fatigue in embrittling environments (although brittle striations are sometimes difficult to resolve owing to their shallow profile and post-fracture corrosion/film formation (Fig. 1).Fatigue crack growth at intermediate ∆K, for both inert and embrittling environments, generally involves plastic blunting and crack growth during the rising load part of each stress cycle, with resharpening of the crack tip occurring by deformation just behind crack tips during unloading. The difference between crack growth in inert and embrittling environments is that slip is more localised for the latter, resulting in less blunting and greater crack-growth increments for a given crack-tipopening displacement (Fig. 2). This figure, and others like it in the literature [e.g. 3,4], omits an important feature, namely, the formation of nanovoids ahead of cracks. Nanovoid formation at intermediate ∆K levels is often overlooked because the presence of nano-scale dimples on fracture surfaces is clearly resolved only when 'state-of-the-art' high-resolution SEM is used [5] or, even better, when TEM is used to examine well-shadowed replicas under ideal conditions [6] (Fig. 3).The localisation of plasticity and increased crack growth rates in both aqueous and gaseous hydrogen environments for many materials (e.g. Fe, Mg, Ni, Ti) are genera...

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Section: Corrosion-fatigue Crack-growth Rates In Steels: Effects Of H...mentioning

confidence: 99%

Effects of Waveform and Cycle Period on Corrosion-Fatigue Crack Growth in Cathodically Protected High-Strength Steels

Knop

Birbilis

Lynch

2014

AMR

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“…It has been demonstrated that the crack path can be changed in a controlled manner by variations in tempering temperature (Davis et al, 1964;Truman et (From Bern stein, 1970. Specifically, it is imperative that the operating crack path be com patible with the steel's microstructure .…”

Section: Thermal and Thermomechanical Treatmentmentioning

confidence: 99%

“…Specifically, it is imperative that the operating crack path be com patible with the steel's microstructure . For ex ample, in a variety of steels, an increasing tempering temperature changes the hydrogen-induced crack path from transgranular to inter granular (Davis et al, 1964;Truman et al, 1964;Lillys and Nehrenberg, 1956). ) al, 1964; Lillys and Nehrenberg, 1956), postanneal cooling rate (Bern stein, 1970;Marquez et al, 1970), and the addition of certain solutes (Rath and Bernstein, 1971;Pressouyre and Bernstein, 1974).…”

Section: Thermal and Thermomechanical Treatmentmentioning

confidence: 99%

Resisting Hydrogen Embrittlement

Bernstein

1976

Alloy and Microstructural Design

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“…[4][5][6][7][8][9] It has been reported that the susceptibility to EAC is greater at higher yield strengths. [1,[10][11][12][13][14][15][16][17][18] Generally, highly acidic conditions promote cracking and highly basic conditions reduce or even prevent cracking. However, over a certain range of pH, there is no great change in susceptibility to EAC.…”

Section: Introductionmentioning

confidence: 99%

Environment-Assisted Cracking in Custom 465 Stainless Steel

Lee¹,

Goswami

Jones³

2010

Metall Mater Trans A

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The influence of cold work and aging on the environment-assisted cracking (EAC) behavior and mechanical properties of Custom 465 stainless steel (SS) was studied. Four sets of specimens were made and tested. All specimens were initially solution annealed, rapidly cooled, and refrigerated (SAR condition). The first specimen set was steel in the SAR condition. The second specimen set was aged to the H1000 condition. The third specimen set was 60 pct cold worked, and the fourth specimen set was 60 pct cold worked and aged at temperatures ranging from 755 K to 825 K (482°C to 552°C) for 4 hours in air. The specimens were subsequently subjected to EAC and mechanical testing. The EAC testing was conducted, using the rising step load (RSL) technique, in aqueous solutions of NaCl of pH 7.3 with concentrations ranging from 0.0035 to 3.5 pct at room temperature. The microstructure, dislocation substructure, and crack paths, resulting from the cold work, aging, or subsequent EAC testing, were examined by optical microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The aging of the cold-worked specimens induced carbide precipitation within the martensite lath, but not at the lath or packet boundaries. In the aged specimens, as aging temperature rose, the threshold stress intensity for EAC (K IEAC ) , elongation, and fracture toughness increased, but the strength and hardness decreased. The K IEAC also decreased with increasing yield strength and NaCl concentration. In the SAR and H1000 specimens, the EAC propagated along the prior austenite grain boundary, while in the cold-worked and cold-worked and aged specimens, the EAC propagated along the martensite lath, and its packet and prior austenite grain boundaries. The controlling mechanism for the observed EAC was identified to be hydrogen embrittlement.

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Stress Corrosion Cracking Study of Several High Strength Steels

Cited by 16 publications

References 0 publications

Effects of Waveform and Cycle Period on Corrosion-Fatigue Crack Growth in Cathodically Protected High-Strength Steels

Effects of Waveform and Cycle Period on Corrosion-Fatigue Crack Growth in Cathodically Protected High-Strength Steels

Resisting Hydrogen Embrittlement

Environment-Assisted Cracking in Custom 465 Stainless Steel

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