Rate Stress Corrosion Cracking Research Articles

Cold Work and Temperature Dependence of Stress Corrosion Crack Growth of Austenitic Stainless Steels in Hydrogenated and Oxygenated High-Temperature Water

Abstract The rate of stress corrosion cracking (SCC) was measured for nonsensitized, cold-worked Type 316 (UNS S31600) and Type 304 (UNS S30400) in both hydrogenated pressurized water reactor (PWR)...

Measurement of plastic strain of polycrystalline material by electron backscatter diffraction

It is important to know the degree of plastic strain in order to evaluate the susceptibility and crack growth rate of stress corrosion cracking (SCC) in stainless steel and nickel based alloy, because SCC is enhanced by the cold work and causes many problems in nuclear power plant components. In this study, electron backscatter diffraction in conjunction with scanning electron microscopy is applied to measure the plastic strain imposed to stainless steel by tensile load. A new parameter, which quantifies the spread of the crystal orientation within individual grains arising due to dislocation accumulation during plastic deformation, is correlated with imposed plastic strain. The new parameter is called ‘crystal deformation’ and is determined from the spread in misorientation from the central grain orientation. It is confirmed that this parameter has a good correlation with plastic strain and is not affected by the data density of the crystal orientation map. The dislocation density distribution is also evaluated from the misorientation from the central orientation. Relatively high dislocation density was observed near grain boundaries and grain boundary triple points, which was consistent with the observed deterioration of EBSD pattern quality in those locations.

Anodic film properties determined by EIS and their relationship with caustic stress corrosion cracking of Alloy 600

The properties of the anodic films formed on Alloy 600 at different applied potentials in 10 wt.% NaOH solution at 315 °C were studied using in situ electrochemical impedance spectroscopy. Relaxation times for passivation and semiconductivity of the films were determined from EIS measurements. The results were correlated with the stress corrosion cracking (SCC) behavior obtained from the C-ring tests under the same conditions. The changes of the semiconductive properties and the peak of relaxation time were observed around 0.20 V where the SCC rate showed a maximum. These results were also consistent with the prediction parameter for SCC obtained from fast and slow polarization scans.

Effect of annealing treatment on the stress corrosion cracking behavior of SiC whisker reinforced aluminum composite

Abstract Stress corrosion cracking (SCC) behavior of SiCw/pure Al or SiCw/2024Al composite in 3.5% NaCl solution was studied using double cantilever beam method. The effect of annealing treatment on SCC behavior of the composites was examined. The results indicated that the annealing treatment had an influence on the SCC properties of the composites. With the increase of the annealing temperature, the threshold stress intensity factor, K ISCC , increased and the steady propagation rate of SCC decreased, so that the SCC susceptibility of composites was improved.

Stress Corrosion Cracking of High-Purity Carbon Steel in Carbonate Solutions

Abstract Slow strain rate tests (SSRT) were performed on a high-purity 0.02% C steel in ammonium carbonate ([NH4]2CO3) solutions at 70°C as a function of applied electrochemical potential. As in previous studies, a narrow critical potential range for fatal cracking in the active-to-passive transition of a rapidly developed polarization curve was observed. At potentials slightly active to the critical potential range, transgranular (TG) and intergranular (IG) fissuring were observed. At potentials noble to the critical range, IG fissuring was observed. Fatigue precracking had no effect on the extent or rate of stress corrosion cracking (SCC), nor did hydrogen embrittlement (HE). Results supported previous theories that IGSCC of carbon steels is the result of a very specific interaction between grain-boundary chemistry and the micromechanics of near-boundary interactions.

Effects of transformation on texture and iodine stress corrosion cracking resistance of zircaloy sheet

A two-step heat treatment was developed as a means of maximizing the basal texture of Zircaloy-4 sheet. The heat treatment, consisting of a brief beta heat treatment and subsequent controlled cooling, resulted in a Kearns number (fn) of 0.83 with a microstructure of uniformly fine grains and high hardness. The texture component, as determined by the crystallite orientation distribution function (CODF), was (0002)(10−10). The result was discussed in terms of phase transformation, either diffusional or martensitic, incurred by controlled cooling. The rate of stress corrosion cracking (SCC) of the alloy was evaluated with constant deflection tests in an iodine environment. The exponentn of the relationshipda/dt = C · (Kln was found to correlate with fn for KI, ranging from 4 to 17 MPa√m.

Slow Strain Rate Stress Corrosion Cracking of AISI 304 Stainless Steel in NaCl Solution and Its Prevention byControlled Cathodic Protection

Abstract The slow strain rate test (SSRT) technique was applied to AISI 304 stainless steel (SS) in neutral and acidic NaCl solutions to define the laboratory test conditions suitable for inducing ...

Effects of H2 Additions on Stress Corrosion Cracking in a Boiling Water Reactor

Abstract Controlled amounts of hydrogen were injected into the Dresden-2 boiling water reactor (BWR) during a five week period. The effect of the hydrogen modifed water chemistry on major structural alloys used in the BWR system was studied. The studies were conducted in a test facility consisting of two 1 L vessels which were piped to receive reactor water from the discharge side of the main recirculation pump. One of the vessels was used to measure electrochemical potentials. The second vessel was used to perform slow strain rate stress corrosion cracking tests. Electrochemical measurements were conducted continuously during normal BWR operation and during periods of hydrogen injection. The hydrogen injection caused the quantity of dissolved oxygen to decrease, which resulted in a substantial drop in corrosion potentials. At the highest injection rate, the corrosion potential of AISI 304 stainless steel dropped below the potential at which intergranular stress corrosion cracking (IGSCC) could be expected. Stress corrosion tests were conducted on severely sensitized AISI 304 stainless steel and pressure vessel steel. During normal operation, the stainless steel failed primarily by IGSCC. During H2 injection when the water contained <20 ppm O2, both IGSCC of the stainless steel and transgranular SCC of pressure vessel steel were eliminated.

Slow Strain Rate Stress Corrosion Cracking under Multiaxial Deformation Conditions: Technique and Application to Admiralty Brass

Abstract A set of straightforward experimental techniques are described for the examination of slow strain rate stress corrosion cracking (SCC) of sheet deforming under nearly all multiaxial deformation conditions which result in sheet thinning. Based on the local fracture strain as a failure criterion, the results contrast the stress corrosion susceptibility in uniaxial tension with those in both plane strain and balanced biaxial tension. As an application of the technique, preliminary results are presented describing the slow strain rate SCC of admiralty brass in an aqueous 0.1 M CuSO4 solution at open circuit potential. These results indicate that the loss of ductility associated with the SCC of the brass increases as the stress state changes from uniaxial toward balanced biaxial tension.

繰返し低ひずみ速度試験による応力腐食割れき裂進展

Sustained load tests were performed on a sensitized high-strength aluminum alloy with repetitional stresses of small amplitude and of constant low strain rate superimposed in 3.5% NaCl solution. The crack growth rate of stress corrosion cracking (SCC) remarkably accelerated under repetitional stresses of a high strain rate K (dynamic SCC), whilst SCC crack growth rate greately decreased under repetitional stresses of a low K owing to the dissolution-induced crack tip blunting. SCC crack growth rate varied much even under a constant K condition. Especially da/dt varied surprisingly under repetitional stresses of a low strain rate K, which may be explained by such a process competition model that one of the processes of fatigue crack growth by repetitional stresses, dissolution-induced crack tip blunting and SCC crack growth by a damage of passive films occurs exclusively.

The Stress Corrosion Cracking of Sensitized Stainless Steel in Thiosulfate Solutions

Abstract The stress corrosion cracking (SCC) of sensitized Type 304 stainless steel in thiosulfate solutions has been studied using constant extension rate tests. Very low concentrations of about 6.10−7M Na2S2O3 (0.1 ppm) gave cracking. With boric acid added, higher concentrations (1 ppm) were required. The SCC was shown to be electrochemically controlled. Below −0.5 VSCE (−0.75SHE) no SCC took place; above this potential, the rate of SCC increased with potential. Straining was required before SCC continued at 0.5 V if the potential was held at or below −0.5 V for extended times.

Crack Initiation in CERT Tests on Type 304 Stainless Steel in Pure Water

Abstract Crack initiation has been determined for Type 304 stainless steel in constant extension rate stress corrosion cracking tests. Tests have been conducted at 125, 200, and 288 C in pure water...

Use of Accelerated Intergranular Corrosion Tests and Pitting Corrosion Tests to Detect Sensitization and Susceptibility to Intergranular Stress Corrosion Cracking in High Temperature Water of Duplex 308 Stainless Steel

Abstract The ability of various intergranular corrosion and pitting corrosion tests to detect sensitization and intergranular stress corrosion cracking susceptibility in high temperature water of duplex 308 stainless steel was evaluated. The duplex alloy contained 10 v/o ferrite and had a specific austenite-ferrite interfacial area of 930 cm2/cm3. The intergranular corrosion resistance of the alloy following 30 different aging treatments was determined in boiling acidified CU-CUSO4 solution (A262E), boiling 65% HNO3 (A262C), and by an electrolytic etch test in 10% oxalic acid (A262A). The pitting corrosion resistance was evaluated by potentiodynamic and galvanostatic tests in 0.1 N HCl at room temperature. The results of all five tests were compared to the results of slow extension rate stress corrosion cracking tests conducted at 550 F in high purity water containing 8 ppm dissolved oxygen. The microstructural features responsible for the corrosion in each test were determined. The A262E test was found to attack the chromium depleted zones in the material. The A262C test preferentially corroded the chromium depleted zones but also dissolved, albeit to a much less extent, the chromium rich phases such as M23C6. The A262A test primarily attacked chromium rich phases. Pitting corrosion was confined to the chromium depleted zones. The results of the A262E test and the galvanostatic pitting test agreed quite closely with the results of the stress corrosion cracking test. There was considerable scatter in the weight loss measurements obtained in the A262C test. The latter could detect the presence of a severely sensitized microstructure but was incapable of distinguishing between mildly sensitized and unsensitized materials. Although pitting was largely confined to the chromium depleted boundaries, unless the sample was severely sensitized, there was considerable scatter in the measured values of the pitting potential. This precluded the use of the latter as a parameter to characterize the degree of sensitization. The A262A test results exhibited the least correlation with the results of the stress corrosion cracking tests. Since the A262A test attacks chromium rich phases such as M23C6, samples which were aged long enough to intergranularly precipitate M23C6 but not long enough to produce chromium depleted zones of sufficient width or contiguity, nevertheless were severely corroded in the A262A test. And samples which were aged long enough to replenish the chromium depleted zones still failed the A262A test because of the continued presence of the chromium rich grain boundary carbides. These tests were also conducted on samples of sensitized and unsensitized austenitic 308 stainless steel. The results were consistent with the findings of the duplex alloy tests.

The Chemical Nature of Aluminum Corrosion: IV. Some Anion Effects on SCC of AA 7075-T651

Abstract Double bolt loaded double cantilever beam specimens were used. Increasing chloride ion concentration increased the stress corrosion cracking (SCC) plateau growth rate up to about 0.6M, presumably by increasing the activation of the aluminum surface; at high concentrations the cracking was slower, perhaps because of lower solubility of oxygen. No analyses or potential measurements were made inside the crack, but nominal external potential and pH values especially for benzoate and ammonium hydroxide indicated that a large potential drop must be obtained within the crack if a hydrogen mechanism is involved, at least in those solutions. The activity of water in aqueous solutions of various salts did not correlate with the SCC rates, indicating that specific ion effects dominated. The nitrate ion is reduced by 7075 to ammonia, though this is slow in concentrated nitrate solution; perchlorate ion was not observed to be reduced to soluble chloride. In general, the substances which activate the aluminum ...

The Effects of Dissolved Oxygen, Chloride Ion and Applied Potential on the SCC Behavior of Type 304 Stainless Steel in 290 C Water

Abstract Slow strain rate stress corrosion cracking (SCC) experiments have been performed on annealed and duplex Type 304 stainless steel in 290 C water. Experimental variables included dissolved oxygen concentration (<1 ppb to 28 ppm), chloride ion concentration (0 to 100 ppm as NaCl), and applied potential and current. Rapid, severe transgranular SCC is observed at 100 ppm chloride when the corrosion potential is shifted over the deaerated threshold potential (−0.15 V vs 0.01 N silver/silver chloride) by adding dissolved oxygen. Likewise, this severe cracking persists in aerated, 100 ppm chloride until cathodic potentials active to the threshold value are applied. However, even at these potentials, some slight cracking persists and is similar in nature to SCC in aerated pure water. At sufficiently active potentials (between −0.25 and −0.40 V), fully ductile failure is observed, and this potential is correlated with a critical oxygen concentration for SCC. Applied anodic currents increase the severity of...

The Effect of Chloride Ion Concentration and Applied Potential on the SCC Behavior of Type 304 Stainless Steel in Deaerated High Temperature Water

Abstract Slow strain rate stress corrosion cracking (SCC) experiments were performed on annealed and duplex Type 304 stainless steel in deaerated, 290 C water. Variables included chloride ion concentration (0 to 1000 ppm as NaCl), applied potential and current, and sensitization. No SCC in any metallurgical condition is observed in chlorides unless potential is applied. Rapid, severe transgranular cracking is observed in chlorides once a threshold anodic potential is reached. For nonsensitized material, this potential was found to correspond exactly to a dynamic pitting potential. Essentially no effect of ferrite on chloride SCC is observed. Sensitized alloys show SCC at considerably more active potentials than homogeneous alloys, and cracking is observed to be intergranular for single phase alloys and interphase for duplex alloys.

Slow strain rate stress corrosion testing at elevated temperatures and high pressures

Slow strain rate stress corrosion cracking experiments have been performed on single phase and duplex phase 304 stainless steels at 290°C. Environmental variables included chloride concentrations (0–1000 ppm), oxygen concentration (0–2 ppm) and potential ( ϕ corr to + 500 mV vs Ag/AgCl). These experiments have shown that s.c.c. resistance is relatively unaffected by Cl − if O 2 concentrations approach zero. However, at 2 ppm O 2 concentration, there is a large decrease in resistance with increasing Cl − concentrations. Anodic polarization of the steels during straining in solutions containing 100 ppm Cl − and 0 ppm O 2 showed a threshold potential for s.c.c. at ∼ 500 mV more noble than the corrosion potential (− 650 ± 60 mV vs Ag/AgCl at temperature).

Application of compliance techniques for studying the effect of side-grooving on stress-corrosion crack kinetics of a high strength steel

Abstract : Sub-critical crack growth was estimated from changes in compliance measured during the stress-corrosion cracking of D6AC steel at constant load using 1-T wedge-opening-loading specimens. Agreement of calculated mean crack growth with mean values measured from the fracture surface showed that plastic yielding at the crack tip during loading and subsequent stress-corrosion cracking was negligible. The analysis was then applied to side-grooved specimens where it was demonstrated that, under plane-strain conditions, side-grooving does not significantly affect the stress-corrosion cracking rate in D6AC steel.

Deformation and fracture behavior of zircaloy-2 deformed at constant strain rate in iodine environment. I. Uniaxial tension test.

The relation between strain rate and iodine stress corrosion cracking (SCC) was studied on Zircaloy-2 subjected to uniaxial stress under constant extension rate in an iodine partial pressure of 4 Torr and at a temperature of 350°C. The specimens were machined from actual fuel cladding tube. In iodine environment, the tangentially directed specimens registered sharp decreases in stress beyond maximum point; this is attributed to crack initiation and propagation. Fracture ductility diminished with decreasing strain rate. Severe SCC was observed at strain rates below 2×10−3min−1. At high strain rates, the mechanism governing the rate of SCC appeared to be the time-dependent corrosion process. The axially directed specimens showed no signs of embrittlement due to gaseous iodine; this is attributed to the particular texture of the Zircaloy. Fracture surface observations indicated that transgranular cleavage fracture along the basal plane appeared to play a significant role in the stages of SCC initiation and p...

Slow Strain Rate Stress Corrosion Cracking of Type 304 Stainless Steels

Abstract Slow strain rate experiments have been performed on Type 304L and 304 stainless steel sheet material in boiling MgCl2 as a function of solution temperature and strain rate. Additionally, s...