The Experts below are selected from a list of 18 Experts worldwide ranked by ideXlab platform
A Turnbull - One of the best experts on this subject based on the ideXlab platform.
-
modelling of Crack Chemistry in sensitized stainless steel in boiling water reactor environments
Corrosion Science, 1997Co-Authors: A TurnbullAbstract:An advanced model has been used to predict the Chemistry and potential in a stress corrosion Crack in sensitized stainless steel in a boiling water reactor (BWR) environment. The model assumes trapezoidal Crack geometry, incorporates anodic reaction and cathodic reduction within the Crack, and takes into account the limited solubility of cations in high temperature water. The results indicate that the Crack tip potential is not independent of the external potential, and that the reactions on the walls of the Crack must be included for reliable prediction. Accordingly, both the modelling assumptions of Ford and Andresen and of Macdonald and Urquidi-Macdonald, whilst having merit, are not fully satisfactory. Extended application of the model for improved prediction of stress corrosion Crack growth rate is constrained by limitations in electrochemical data which are currently inadequate.
L.m. Young - One of the best experts on this subject based on the ideXlab platform.
-
Characterization of the roles of electroChemistry, convection and Crack Chemistry in stress corrosion Cracking
1995Co-Authors: Peter L. Andresen, L.m. YoungAbstract:Understanding the role of ionic current flow within a Crack and near the Crack tip is fundamental to modeling of environmentally assisted Crack advance. Critical conceptual issues and models related to ionic current flow within Cracks, and the associated ``crevice`` Chemistry and metal oxidation that results, are presented and examined in the light of experimental evidence. Various advanced techniques have been developed to evaluate the roles of electroChemistry, transport, and Crack Chemistry in stress corrosion Cracking, with emphasis on high temperature ``pure`` water. These include high resolution Crack length measurement by dc potential drop performed simultaneously with microsampling, electrochemical microprobe mapping, microinjection of species, and micropolarization of the Crack. Conceptual issues addressed include the importance of the corrosion potential vs. oxidant concentration, the absence of oxidants and associated low corrosion potential within Cracks, the location and role of macrocell currents associated with potential gradients from differential aeration cells, the localized nature of the microcell currents associated with dissolution at the Crack tip, the importance of pH and adsorbed species on repassivation and Crack advance, and the role of convection in Crack Chemistry and Crack advance. Correct concepts are shown to be an essential pre-cursor to quantitative modeling.
Richard P Gangloff - One of the best experts on this subject based on the ideXlab platform.
-
Crack Chemistry control of intergranular stress corrosion Cracking in sensitized al mg
Corrosion, 2015Co-Authors: Cortney B Crane, Robert G. Kelly, Richard P GangloffAbstract:Fracture mechanics experiments and occluded Crack Chemistry modeling validate the mechanism for intergranular stress corrosion Cracking (IGSCC) of sensitized Al-Mg alloys: dissolution of discontinuous grain boundary β (Al3Mg2) precipitates activates Al-Mg (α) solid solution dissolution to acidify the Crack solution for Crack tip hydrogen embrittlement. Slow-rising displacement experiments with preCracked specimens establish the strong effect of applied potential on IGSCC kinetics for sensitized AA5083-H131 (S-L orientation, 22 mg/cm2) in neutral NaCl solution. Anodic polarization increases growth rates through enhanced α dissolution for Crack acidification and H uptake, whereas cathodic polarization below the pH-sensitive α breakdown potential reduces growth rates by limiting Al dissolution, and thus Crack acidification and the overpotential for H production (ηH). Polarization below the β breakdown potential eliminates IGSCC by precluding β dissolution and Crack acidification. Cathodic polarization could ...
Robert G. Kelly - One of the best experts on this subject based on the ideXlab platform.
-
Crack Chemistry control of intergranular stress corrosion Cracking in sensitized al mg
Corrosion, 2015Co-Authors: Cortney B Crane, Robert G. Kelly, Richard P GangloffAbstract:Fracture mechanics experiments and occluded Crack Chemistry modeling validate the mechanism for intergranular stress corrosion Cracking (IGSCC) of sensitized Al-Mg alloys: dissolution of discontinuous grain boundary β (Al3Mg2) precipitates activates Al-Mg (α) solid solution dissolution to acidify the Crack solution for Crack tip hydrogen embrittlement. Slow-rising displacement experiments with preCracked specimens establish the strong effect of applied potential on IGSCC kinetics for sensitized AA5083-H131 (S-L orientation, 22 mg/cm2) in neutral NaCl solution. Anodic polarization increases growth rates through enhanced α dissolution for Crack acidification and H uptake, whereas cathodic polarization below the pH-sensitive α breakdown potential reduces growth rates by limiting Al dissolution, and thus Crack acidification and the overpotential for H production (ηH). Polarization below the β breakdown potential eliminates IGSCC by precluding β dissolution and Crack acidification. Cathodic polarization could ...
-
The Correlation Between Crack Chemistry and Crack Growth Behavior of 7XXX Series Aluminum Alloys: A Comparison of Field and Laboratory Tests
Corrosion, 1999Co-Authors: Kevin R Cooper, Robert G. Kelly, Edward L. ColvinAbstract:The Crack growth kinetics and solution Chemistry developed within environment-assisted Cracks (EAC) grown in laboratory tests and long-term field exposures of high-strength A1-Zn-Mg-Cu alloys were assessed. For both test programs, peak-aged (T651) material exhibited Crack growth kinetics 10{sup 3} to 10{sup 4} times that of overaged (T7X51). Laboratory Crack growth studies in aqueous CrO{sub 4}{sup 2{minus}}/Cl{sup {minus}} environments demonstrated the characteristic enhanced resistance of overaged A1-Zn-Mg-Cu alloys to intergranular EAC Crack propagation relative to peak-aged tempers. The laboratory environment is suitable for alloy development and mechanistic studies of environment-assisted Cracking in these alloys. Cracks within fracture specimens exposed to an industrial atmosphere contained predominantly chloride and sulfate with minor amounts of nitrate, nitrite and organic acids. The dominant cations found were aluminum, zinc and magnesium dissolved from the alloy in addition to sodium and potassium from the external atmosphere. Environment-assisted Crack growth behavior during atmospheric exposure was not correlated to the Crack Chemistry. The Crack solution of field-exposed specimens was similar for peak-aged and overaged material, attaining a pH of 3 to 3.8. The Crack solution of these specimens was probably dominated by crevice corrosion. In contrast to the atmospheric tests, the low corrosiveness of the laboratory environment facilitated differentiationmore » of peak-aged and overaged Crack Chemistry. Whereas peak-aged material developed an acidic, concentrated Al-salt solution at the Crack tip, overaged material showed little alteration of the Crack environment from that of the external solution.« less
C R M Grovenor - One of the best experts on this subject based on the ideXlab platform.
-
high resolution imaging of complex Crack Chemistry in reactor steels by nanosims
Journal of Nuclear Materials, 2008Co-Authors: Sergio Lozanoperez, Matt R Kilburn, T Yamada, T Terachi, C A English, C R M GrovenorAbstract:High-resolution analysis using a Cameca NanoSIMS 50 has been used to map the oxide Chemistry in intergranular Cracks in stainless steels. The technique has proven ideal for this type of sample, as it is able to discern between the different oxide layers and clarify the role of minor segregants such as boron and sulphur. Results are compared with analysis of the same sample by scanning auger microscopy and its interpretation discussed. The short time required to prepare and examine multiple regions present the NanoSIMS as an optimum tool for corrosion characterization.
