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Environment-assisted-cracking under measured and/or controlled ectrochemical potential

Description: Longer-term stress corrosion cracking (SCC) experiments, described in the activity plan E-20-56, are well underway at LLNL to evaluate the SCC susceptibility of candidate corrosion-resistant inner container materials in a 90°ºC acidic brine containing 5 weight percent (wt%) NaCl using fatigue-precracked wedge-loaded double-cantilever-beam (DCB) specimens. The results of a recent localized corrosion study have revealed that the propensity to pitting and crevice corrosion in susceptible alloys is characterized by "critical potentials" obtained from the cyclic potentiodynamic polarization (CPP) experiments described in the activity plan E-20-43/44. It is also well known that the tendency to SCC can be influenced by the electrochemical potential. But the role of electrochemistry in SCC has not been explored to a large extent. Therefore, the proposed activity is aimed at evaluating the SCC behavior of susceptible container materials under measured and/or controlled electrochemical potential in repository-relevant environments using DCB and slow-strain-rate (SSR) test specimens. The magnitude of the controlled potential will be selected based on the measured "critical potentials" obtained from the CPP experiment performed earlier in a similar environment. The resultant data will enable the mechanistic understanding of the cracking process in materials of interest under the synergistic influence of applied stress and corrosive medium, which will be utilized in developing and validating the SCC models for long-term performance assessment.
Date: November 7, 1997
Creator: Roy, A.
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking tests using double-cantilever-beam specimens

Description: Although a wide variety of degradation modes can occur in aqueous environments for corrosion-resistant metallic materials, localized corrosion such as pitting corrosion, crevice corrosion, SCC, and hydrogen embrinlement (HE) is considered to be the primary mode. The evaluation of the susceptibility of candidate corrosion-resistant container materials to pitting and crevice corrosion is well underway using electrochemical polarization techniques described in the Activity Plan E-20-43144. The proposed activity (E-20-56) is aimed at evaluating the SCC behavior of these materials in susceptible environments using the linearelastic-fracture-mechanics (LEFM) concept. The mechanical driving force for crack growth, or the stress distribution at the crack tip is quantified by the stress intensity factor, K, for the specific crack and loading geometry. The critical stress intensity factor for SCC, K<sub>ISCC</sub> for candidate materials will be evaluated in environments of interest, and their comparisons will be made to select the waste package inner container material having an optimum SCC resistance.
Date: October 25, 1996
Creator: Roy, A.
Partner: UNT Libraries Government Documents Department

De-alloying and stress corrosion cracking. Final report, July 1, 1990--June 30, 1993

Description: Results of work on fracture properties of porous dealloyed gold structures indicates that this material undergoes a brittle-ductile transition as the size scale of the porosity increases. Aspects of the work reported on and proposed address fundamental issues related corrosion in alloy systems. De-alloyed film induce brittle fracture experiments are being performed on Ag-Au and Cu-Au alloy thin sheets. An indirect potential drop technique is being developed to measure dynamic crack motion. Preliminary work is being performed to determine optimum conditions for film thickness-crack penetration experiments.
Date: April 1, 1996
Creator: Sieradzki, K.
Partner: UNT Libraries Government Documents Department

Implications of early stages in the growth of stress corrosion cracking on component reliability

Description: Environment-induced crack growth generally progresses through several stages prior to component failure. Crack initiation, short crack growth, and stage 1 growth are early stages in crack development that are summarized in this paper. The implications of these stages on component reliability, derive from the extended time that the crack exists in the early stages because crack velocity is slow. The duration of the early stages provides a greater opportunity for corrective action if cracks can be detected. Several important factors about the value of understanding short crack behavior include: (1) life prediction requires a knowledge of the total life cycle of the crack including the early stages, (2) greater reliability is possible if the transition between short and long crack behavior is known component life after this transition is short and (3) remedial actions are more effective for short than long cracks.
Date: April 1, 1995
Creator: Jones, R.H. & Simonen, E.P.
Partner: UNT Libraries Government Documents Department

An Investigation of the Mechanism of IGA/SCC of Alloy 500 in Corrosion Accelerating Heated Crevice Environments. Technical progress report

Description: OAK-B135 An Investigation of the Mechanism of IGA/SCC of Alloy 500 in Corrosion Accelerating Heated Crevice Environments. Technical progress report Note: This report was submitted electronically even though Part II A indicates by ''PAPER''.
Date: March 1, 2000
Creator: Lumsden, Jesse
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking behavior of Alloy 600 in high temperature water

Description: SCC susceptibility of Alloy 600 in deaerated water at 360 C (statically loaded U-bend specimens) is dependent on microstructure and whether the material was cold-worked and annealed (CWA) or hot-worked and annealed (HWA). All cracking was intergranular, and materials lacking grain boundary carbides were most susceptible to SCC initiation. CWA tubing materials are more susceptible to SCC initiation than HWA ring-rolled forging materials with similar microstructures (optical metallography). In CWA tubing materials, one crack dominated and grew to a visible size. HWA materials with a low hot-working finishing temperature (<925 C) and final anneals at 1010-1065 C developed both large cracks (similar to those in CWA materials) and small intergranular microcracks detectable only by destructive metallography. HWA materials with a high hot-working finishing temperature (>980 C) and a high-temperature final anneal (>1040 C), with grain boundaries that are fully decorated, developed only microcracks in all specimens. These materials did not develop large, visually detectable cracks, even after more than 300 weeks exposure. A low-temperature thermal treatment (610 C for 7h), which reduces or eliminates SCC in Alloy 600, did not eliminate microcrack formation in high temperature processed HWA materials. Conventional metallographic and analytical electron microscopy (AEM) were done on selected materials to identify the factors responsible for the observed differences in cracking behavior. Major difference between high-temperature HWA and low-temperature HWA and CWA materials was that the high temperature processing and final annealing produced predominantly ``semi-continuous`` dendritic M{sub 7}C{sub 3} carbides along grain boundaries with a minimal amount of intragranular carbides. Lower temperature processing produced intragranular M7C3 carbides, with less intergranular carbides.
Date: July 1, 1995
Creator: Webb, G.L. & Burke, M.G.
Partner: UNT Libraries Government Documents Department

Stress-corrosion fatigue-crack growth in a Zr-based bulk amorphousmetal

Description: Electrochemical and mechanical experiments were conducted to analyze the environmentally-influenced cracking behavior of a bulk amorphous metal, Zr41.2Ti13.8Cu12.5Ni10Be22.5. This study was motivated by a scientific interest in mechanisms of fatigue-crack propagation in an amorphous metal, and by a practical interest in the use of this amorphous metal in applications that take advantage of its unique properties, including high specific strength, large elastic strains and low damping. The objective of the work was to determine the rate and mechanisms of subcritical crack growth in this metallic glass in an aggressive environment. Specifically, fatigue-crack propagation behavior was investigated at a range of stress intensities in air and aqueous salt solutions by examining the effects of loading cycle, stress-intensity range, solution concentration, anion identity, solution de-aeration, and bulk electrochemical potential. Results indicate that crack growth in aqueous solution in this alloy is driven by a stress-assisted anodic reaction at the crack tip. Rate-determining steps for such behavior are reasoned to be electrochemical, stress-dependent reaction at near-threshold levels, and mass transport at higher (steady-state) growth rates.
Date: September 21, 2005
Creator: Schroeder, V. & Ritchie, R. O.
Partner: UNT Libraries Government Documents Department


Description: High concentration caustic solutions are known to cause stress corrosion cracking in carbon steel at elevated temperature. This calculation establishes the conditions where heat of dilution will not cause the solution temperature--concentration to exceed the boundary for stress corrosion cracking as established by NACE International.
Date: February 20, 2007
Creator: Barton, W. B.
Partner: UNT Libraries Government Documents Department

The Effect of Weld Residual Stress on Life of Used Nuclear Fuel Dry Storage Canisters

Description: With the elimination of Yucca Mountain as the long-term storage facility for spent nuclear fuel in the United States, a number of other storage options are being explored. Currently, used fuel is stored in dry-storage cask systems constructed of steel and concrete. It is likely that used fuel will continue to be stored at existing open-air storage sites for up to 100 years. This raises the possibility that the storage casks will be exposed to a salt-containing environment for the duration of their time in interim storage. Austenitic stainless steels, which are used to construct the canisters, are susceptible to stress corrosion cracking (SCC) in chloride-containing environments if a continuous aqueous film can be maintained on the surface and the material is under stress. Because steel sensitization in the canister welds is typically avoided by avoiding post-weld heat treatments, high residual stresses are present in the welds. While the environment history will play a key role in establishing the chemical conditions for cracking, weld residual stresses will have a strong influence on both crack initiation and propagation. It is often assumed for modeling purposes that weld residual stresses are tensile, high and constant through the weld. However, due to the strong dependence of crack growth rate on stress, this assumption may be overly conservative. In particular, the residual stresses become negative (compressive) at certain points in the weld. The ultimate goal of this research project is to develop a probabilistic model with quantified uncertainties for SCC failure in the dry storage casks. In this paper, the results of a study of the residual stresses, and their postulated effects on SCC behavior, in actual canister welds are presented. Progress on the development of the model is reported.
Date: August 1, 2013
Creator: Ballinger, Ronald G.; Ferry, Sara E.; Black, Bradley P. & Teysseyre, Sebastien P.
Partner: UNT Libraries Government Documents Department


Description: In this study, the effects of laser shock peening (LSP) on stress corrosion cracking (SCC) behavior of Alloy 600 in tetrathionate solution were investigated. The degree of sensitization was quantified using double loop electrochemical potentiokinetic reactivation (DLEPR) tests. The sensitized Alloy 600 was demonstrated to be susceptible to intergranular SCC in tetrathionate solution. Following LSP, residual stresses and the amount of plastic strain introduced in Alloy 600 were characterized. The effects of LSP on SCC susceptibility of Alloy 600 in tetrathionate solution were evaluated by slow strain rate tests and constant load tests. Results indicate a significant increase in resistance to crack initiation and decreased susceptibility to SCC after LSP.
Date: August 1, 2013
Creator: Telang, Abhishek; Gill, Amrinder; S.R.Mannava; Vasudevan, Vijay K.; Qian, Dong & Teysseyre, Sebastien P.
Partner: UNT Libraries Government Documents Department

Strees Corrosion Cracking Initiation of Ni-Bassed Alloys in High Temperature Water

Description: The goal of the work is to provide stress corrosion cracking (SCC) initiation data for Alloy 600 that is not compromised by (1) specimens that suffer from stress relaxation, (2) specimens which have an unknown stress state, (3) specimens which are tested at unknown positions electrochemically relative to the Ni/NiO phase transition, and (4) testing which relies on the period of time between specimen inspection intervals to estimate SCC initiation times. The current study was aimed at studying the effects of temperature and coolant hydrogen concentration on SCC initiation in high purity, high temperature water.
Date: March 21, 2005
Creator: Richey, E & Morton, D
Partner: UNT Libraries Government Documents Department

Experimental Evaluation of Tude Support Plate Crevice Chemistry

Description: A test methodology for measuring temperature, impedance, pH, and electrochemical potential distributions within a sludge-packed tube support plate crevice in a laboratory test is described. The method successfully showed that there were large concentration gradients between the tube and tube support plate sides of the crevice. The testing also showed that strong bases concentrated more effectively than strong acids, and that the crevice pH, when exposed to seawater-based solutions, increased with increasing superheat and decreasing bulk concentration. The large variations in the crevice chemistry observed under heat transfer were eliminated upon shutdown. These new test data suggest that it might be beneficial to evaluate the variation in the extent of stress corrosion cracking with tube support plate elevation found in some steam generators in light of local chemistry changes, as well as the variation in tubing temperature. Because of the large crevice chemistry gradients during boiling heat transfer and their subsequent homogenization upon test shutdown, the results suggest reassessing the use of hideout return measurements and tube deposit analyses in industry to infer the crevice chemistry under heat transfer conditions.
Date: May 8, 2001
Creator: Baum, Allen
Partner: UNT Libraries Government Documents Department

The Application of Reliability-Based Design Factors In Stress Corrosion Cracking Evaluations

Description: First-order reliability methodology (FORM) is used to develop reliability-based design factors for deterministic analyses of stress corrosion cracking. The basic elements of FORM as applied to structural reliability problems are reviewed and then employed specifically to stress corrosion cracking evaluations. Failure due to stress corrosion cracking is defined as crack initiation followed by crack growth to a critical depth. The stress corrosion cracking process is thus represented in terms of a crack initiation time model and a crack growth rate model, with the crack growth rate integrated from the initiation time to the time at which the crack grows to its critical depth. Both models are described by log-normal statistical distribution functions. A procedure is developed to evaluate design factors that are applied to the mean values of the crack initiation time and the crack growth rate for specified temperature and stress conditions. The design factors, which depend on the standard deviations of the statistical distributions, are related to a target reliability, which is inversely related to an acceptable probability of failure. The design factors are not fixed, but are evaluated on a case-to-case basis for each application. The use of these design factors in a deterministic analysis assures that the target reliability will be attained and the corresponding acceptable probability of failure will not be exceeded. An example problem illustrates use of this procedure.
Date: December 20, 2001
Creator: Friedman, E.
Partner: UNT Libraries Government Documents Department

Materials Degradation and Detection (MD2): Deep Dive Final Report

Description: An effort is underway at Pacific Northwest National Laboratory (PNNL) to develop a fundamental and general framework to foster the science and technology needed to support real-time monitoring of early degradation in materials used in the production of nuclear power. The development of such a capability would represent a timely solution to the mounting issues operators face with materials degradation in nuclear power plants. The envisioned framework consists of three primary and interconnected “thrust” areas including 1) microstructural science, 2) behavior assessment, and 3) monitoring and predictive capabilities. A brief state-of-the-art assessment for each of these core technology areas is discussed in the paper.
Date: February 1, 2013
Creator: McCloy, John S.; Montgomery, Robert O.; Ramuhalli, Pradeep; Meyer, Ryan M.; Hu, Shenyang Y.; Li, Yulan et al.
Partner: UNT Libraries Government Documents Department

Localized Deformation as a Primary Cause of Irradiation Assisted Stress Corrosion Cracking

Description: The objective of this project is to determine whether deformation mode is a primary factor in the mechanism of irradiation assisted intergranular stress corrosion cracking of austenitic alloys in light watert reactor core components. Deformation mode will be controlled by both the stacking fault energy of the alloy and the degree of irradiation. In order to establish that localized deformation is a major factor in IASCC, the stacking fault energies of the alloys selected for study must be measured. Second, it is completely unknown how dose and SFE trade-off in terms of promoting localized deformation. Finally, it must be established that it is the localized deformation, and not some other factor that drives IASCC.
Date: March 31, 2009
Creator: Was, Gary S.
Partner: UNT Libraries Government Documents Department


Description: The DOE Complex is packaging plutonium-bearing materials for storage and eventual disposition or disposal. The materials are handled according to the DOE-STD-3013 which outlines general requirements for stabilization, packaging and long-term storage. The storage vessels for the plutonium-bearing materials are termed 3013 containers. Stress corrosion cracking has been identified as a potential container degradation mode and this work determined that the residual stresses in the containers are sufficient to support such cracking. Sections of the 3013 outer, inner, and convenience containers, in both the as-fabricated condition and the closure welded condition, were evaluated per ASTM standard G-36. The standard requires exposure to a boiling magnesium chloride solution, which is an aggressive testing solution. Tests in a less aggressive 40% calcium chloride solution were also conducted. These tests were used to reveal the relative stress corrosion cracking susceptibility of the as fabricated 3013 containers. Significant cracking was observed in all containers in areas near welds and transitions in the container diameter. Stress corrosion cracks developed in both the lid and the body of gas tungsten arc welded and laser closure welded containers. The development of stress corrosion cracks in the as-fabricated and in the closure welded container samples demonstrates that the residual stresses in the 3013 containers are sufficient to support stress corrosion cracking if the environmental conditions inside the containers do not preclude the cracking process.
Date: November 10, 2009
Creator: Mickalonis, J. & Dunn, K.
Partner: UNT Libraries Government Documents Department