Download or read book Stress Corrosion Cracking and Crack Tip Characterization of Alloy X 750 in Light Water Reactor Environments written by Jonathan Paul Gibbs and published by . This book was released on 2011 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stress corrosion cracking (SCC) susceptibility of Inconel Alloy X-750 in the HTH condition has been evaluated in high purity water at 93 and 288°C under Boiling Water Reactor Normal Water Chemistry (NWC) and Hydrogen Water Chemistry (HWC) conditions. SCC crack growth rates of approximately 1.1 x 10-7 mm/s (K=28 MPa[square root symbol]m) under NWC conditions and 1.4xI 0-8 mm/s (K=28 MPa[square root symbol]m) under HWC in high purity water at 288°C were observed. The environmental conditions were changed from NWC to HWC during constant K loading, and the crack growth rate immediately slowed down by approximately one order of magnitude. The alloy was also tested in HWC at 93°C. No SCC crack growth was observed at K= 35 MPa[square root symbol]m for the length of time tested at 93°C. The fracture mode transitioned from predominantly transgranular cracking under fatigue conditions to a mixture of intergranular, pseudo-intergranular, and a small amount of transgranular fracture in constant stress intensity SCC. Pseudo-intergranular cracking is when a crack propagates directly adjacent to the grain boundary carbides and not actually on the grain boundary. The SCC crack tips were characterized with scanning electron microscopy (SEM) and 3D Atom Probe Tomography (APT). The SEM analysis was focused on the fractographic analysis and crack-propagation mode. The crack was observed to propagate adjacent to grain boundary carbides (pseudo-intergranular) and along a boundary with high coherency where no carbides were present (intergranular). The small and localized areas of transgranular cracking were occasionally seen between two regions of intergranular cracking. The APT reconstructions of the crack tips and crack wall identified several key features contributing to the SCC process: 1) Preferential oxygen transport occurs in either a finger-like or crystallographic morphology extending from the crack tip region. These regions are enriched in both oxygen and oxide with the oxide being a chromium-nickel spinel. 2) The matrix ahead of each finger-like "tunnel" is enriched in oxygen and predominantly chromium oxide. This indicates that oxygen is diffusing ahead of the crack tip into the bulk material. 3) The oxygen that penetrates directly into the base material from the crack walls in an ordered manner suggests that it is controlled by crystallographic features. 4) The main SCC crack tip is full of predominantly oxide phase and, to a lesser extent, metal atoms. The very crack tip forms a spinel of chromium and nickel oxides. Iron oxide begins to contribute to the oxide spinel approximately 25-30 nm from the actual tip. 5) The [gamma] precipitates that are directly adjacent to each crack tip and crack wall were deficient in aluminum content. The aluminum content in the bulk [gamma] was approximately 6.6 at% and the near-crack [gamma] aluminum content ranged from 2.5-3.5 at%. The range of affected [gamma] was approximately 100 nm wide.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1989 with total page 1332 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of the Environment on the Initiation of Crack Growth written by William Alan Van der Sluys and published by ASTM International. This book was released on 1997 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Corrosion Issues in Light Water Reactors written by D Féron and published by Elsevier. This book was released on 2007-06-22 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stress corrosion cracking is a major problem in light water nuclear reactors, whether pressurised water reactors (PWRs) or boiling water reactors (BWRs). The nuclear industry needs to be able to predict the service life of these power plants and develop appropriate maintenance and repair practices to ensure safe long term operation. This important book sums up key recent research on corrosion in light water reactors and its practical applications.The book is divided into four parts. It begins with an overview of materials degradation due to stress corrosion, corrosion potential monitoring and passivation. Part two summarises research on susceptibility of materials to stress corrosion cracking and the ways it can be initiated. The third part of the book considers stress corrosion crack propagation processes whilst the final part includes practical case studies of corrosion in particular plants. The book reviews corrosion in a range of materials such as low alloy steels, stainless steels and nickel-based alloys.With its distinguished editor and team of contributors, Corrosion issues in light water reactors is a standard work for the nuclear industry. - Summarises key recent research on corrosion in light water reactors - Includes practical case studies

Download or read book Analysis of Alloy 600 and X 750 Stress Corrosion Cracks written by C. Thompson and published by . This book was released on 1993 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stress corrosion Cracking in High Strength Steels and in Titanium and Aluminum Alloys written by Benjamin Floyd Brown and published by . This book was released on 1972 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stress Corrosion Cracking Of Metals A State of the Art written by H. Lee Craig and published by ASTM International. This book was released on 1972 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stress corrosion Cracking written by Russell H. Jones and published by ASM International(OH). This book was released on 1992 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt: Details the many conditions under which stress-corrosion cracking (SCC) can occur, the parameters which control SCC, and the methodologies for mitigating and testing for SCC, plus information on mechanisms of SCC with experimental data on a variety of materials. Contains information about environmen

Download or read book Prediction of Pure Water Stress Corrosion Cracking PWSCC in Nickel Base Alloys Using Crack Growth Rate Models written by and published by . This book was released on 1995 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Ford/Andresen slip dissolution SCC model, originally developed for stainless steel components in BWR environments, has been applied to Alloy 600 and Alloy X-750 tested in deaerated pure water chemistry. A method is described whereby the crack growth rates measured in compact tension specimens can be used to estimate crack growth in a component. Good agreement was found between model prediction and measured SCC in X-750 threaded fasteners over a wide range of temperatures, stresses, and material condition. Most data support the basic assumption of this model that cracks initiate early in life. The evidence supporting a particular SCC mechanism is mixed. Electrochemical repassivation data and estimates of oxide fracture strain indicate that the slip dissolution model can account for the observed crack growth rates, provided primary rather than secondary creep rates are used. However, approximately 100 cross-sectional TEM foils of SCC cracks including crack tips reveal no evidence of enhanced plasticity or unique dislocation patterns at the crack tip or along the crack to support a classic slip dissolution mechanism. No voids, hydrides, or microcracks are found in the vicinity of the crack tips creating doubt about classic hydrogen related mechanisms. The bulk oxide films exhibit a surface oxide which is often different than the oxides found within a crack. Although bulk chromium concentration affects the rate of SCC, analytical data indicates the mechanism does not result from chromium depletion at the grain boundaries. The overall findings support a corrosion/dissolution mechanism but not one necessarily related to slip at the crack tip.

Download or read book Stress Corrosion Crack Growth Rate Testing and Analytical Electron Microscopy of Alloy 600 as a Function of Pourbaix Space and Microstructure written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Stress corrosion crack (SCC) growth rate tests and analytical electron microscopy (AEM) studies were performed over a broad range of environments and heat treatments of Alloy 600. This effort was conducted to correlate bulk environmental conditions such as pH and electrochemical potential (EcP) with the morphology of the SCC crack. Development of a library of AEM morphologies formed by SCC in different environments is an important step in identifying the conditions that lead to SCC in components. Additionally, AEM examination of stress corrosion cracks formed in different environments and microstructures lends insight into the mechanism(s) of stress corrosion cracking. Testing was conducted on compact tension specimens in three environments: a mildly acidic oxidizing environment containing sulfate ions, a caustic environment containing 10% NaOH, and hydrogenated near-neutral buffered water. Additionally, stress corrosion cracking testing of a smooth specimen was conducted in hydrogenated steam. The following heat treatments of Alloy 600 were examined: mill annealed at 980 C (near-neutral water), mill annealed at 1010 C (steam), sensitized (acid and caustic), and mill annealed + healed to homogenize the grain boundary Cr concentration (caustic). Crack growth rate (CGR) testing showed that sensitized Alloy 600 tested in the mildly acidic, oxidizing environment containing sulfate ions produced the fastest cracking (≈ 8.8 [mu]m/hr at 260 C), and AEM examination revealed evidence of sulfur segregation to the crack tip. The caustic environment produced slower cracking (≈ 0.4 [mu]m/hr at 307 C) in the mill annealed + healed heat treatment but no observed cracking in the sensitized condition. In the caustic environment, fully oxidized carbides were present in the crack wake but not ahead of the crack tip. In near-neutral buffered water at 338 C, the CGR was a function of dissolved hydrogen in the water and exhibited a maximum (0.17 [mu]m/hr) near the transition between Ni and NiO stability. The cracks in near-neutral hydrogenated water exhibited Cr-rich spinels and NiO-type oxides but no significant oxidation of grain boundary carbides. No clear effect of dissolved hydrogen on the crack wake morphology was apparent. In hydrogenated steam testing of a smooth specimen (CGR estimated as ≈ 0.7 [mu]m/hr at 399 C), metallic nickel nodules were evident in both the crack wake and on the specimen surface. Oxide particles having a similar size and shape to the microstructural carbides were found in the crack wake, suggesting that these particles are carbides that were oxidized by contact with the steam. The present results show that different environments often produce unique crack tip morphologies that can be identified via AEM.

Download or read book Strain Energy Density distance Criterion for the Initiation of Stress Corrosion Cracking of Alloy X 750 written by and published by . This book was released on 1996 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: A strain energy density-distance criterion was previously developed and used to correlate rising-load K{sub c} initiation data for notched and fatigue precracked specimens of hydrogen precharged Alloy X-750. This criterion, which was developed for hydrogen embrittlement (HE) cracking, is used here to correlate static-load stress corrosion cracking (SCC) initiation times obtained for smooth geometry, notched and fatigue precracked specimens. The onset of SCC crack growth is hypothesized to occur when a critical strain, which is due to environment-enhanced creep, is attained within the specimen interior. For notched and precracked specimens, initiation is shown by analysis to occur at a variable distance from notch and crack tips. The initiation site varies from very near the crack tip, for highly loaded sharp cracks, to a site that is one grain diameter from the notch, for lower loaded, blunt notches. The existence of hydrogen gradients, which are due to strain-induced hydrogen trapping in the strain fields of notch and crack tips, is argued to be controlling the site for initiation of cracking. By considering the sources of the hydrogen, these observations are shown to be consistent with those from the previous HE study, in which the characteristic distance for crack initiation was found to be one grain diameter from the notch tip, independent of notch radius, applied stress intensity factor and hydrogen level.

Download or read book Inhibition of Stress Corrosion Cracking of Alloy X 750 by Prestrain written by and published by . This book was released on 1997 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tests of precracked and as-notched compact tension specimens were conducted in 3600C hydrogenated water to determine the effect of prestrain on the stress corrosion cracking (SCC) resistance of Alloy X-750 in the HTH, AH and HOA heat treated conditions. Prestraining is defined as the intentional application of an initial load (or strain) that is higher than the final test load. Prestrain was varied from 10% to 40% (i.e., the initial to final load ratios ranged from 1.1 to 1.4). Other variables included notch root radius, stress level and irradiation. Specimens were bolt-loaded to maintain essentially constant displacement conditions during the course of the test. The frequent heat up and cooldown cycles that were necessary for periodic inspections provided an opportunity to evaluate the effect of test variables on rapid low temperature crack propagation to which this alloy is subject. For Condition HTH, application of 20% to 40% prestrain either eliminates or significantly retards SCC initiation in as-notched specimens and the onset of crack growth in precracked specimens. In addition, this procedure reduces the propensity for low temperature crack growth during cooldown. Similar results were observed for precracked HOA specimens. Application of 20% prestrain also retards SCC in as-notched and precracked AH specimens, but the effects are not as great as in Condition HTH. Prestraining at the 10% level was found to produce an inconsistent benefit. In-reactor SCC testing shows that prestrain greatly improves the in-flux and out-of-flux SCC resistance of Condition HTH material. No SCC was observed in precracked specimens prestrained 30%, whereas extensive cracking was observed in their nonprestrain counterparts.

Download or read book Metals Abstracts written by and published by . This book was released on 1994 with total page 1584 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanism of Stress corrosion Cracking of Alloy X 750 in High Purity Water written by C. A. Grove and published by . This book was released on 1985 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue and Environmentally Assisted Cracking in Light Water Reactors written by and published by . This book was released on 1992 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue and stress corrosion cracking (SCC) for low-alloy steel used in piping and in steam generator and reactor pressure vessels have been investigated. Fatigue data were obtained on medium-sulfur-content A533-Gr B and A106-Gr B steels in high-purity (HP) deoxygenated water, in simulated pressurized water reactor water, and in air. Analytical studies focused on the behavior of carbon steels in boiling water reactor (BWR) environments. Crack-growth rates of composite fracture-mechanics specimens of A533-Gr B/Inconel-182/Inconel-600 (plated with nickel) and homogeneous specimens of A533-Gr B steel were determined under small-amplitude cyclic loading in HP water with ≈300 pbb dissolved oxygen. Radiation-induced segregation and irradiation-assisted SCC of Type 304 SS after accumulation of relatively high fluence also have been investigated. Microchemical and microstructural changes in HP and commercial-purity Type 304 SS specimens from control-blade absorber tubes used in two operating BWRs were studied by Auger electron spectroscopy and scanning electron microscopy, and slow-strain-rate tensile tests were conducted on tubular specimens in air and in simulated BWR water at 289°C.

Download or read book Mechanisms of Stress Corrosion Cracking and Liquid Metal Embrittlement Particularly in High Strength Aluminium Alloys written by S. P. Lynch and published by . This book was released on 1977 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metallographic and fractographic observations of sub-critical crack growth in a precipitation-hardened AlZn-Mg alloy in liquid-metal, aqueous, and water-vapour/air environments suggest that stress-corrosion cracking and liquid-metal embrittlement in this alloy involve a common mechanism. Sub-critical crack growth in all these environments can produce entirely dimpled fracture surfaces and, in liquid-metal and aqueous environments, crack growth can occur extremely rapidly. It is proposed that stress-corrosion cracking and liquid-metal embrittlement in aluminium alloys (and possibly other materials) can be explained on the basis that chemisorption of environmental species facilitates nucleation of dislocations at crack tips. Such a process would produce sub-critical crack growth with less blunting at crack tips than in inert environments and, hence, would explain observations that dimples on fracture surfaces after SCC are smaller and shallower than those on overload fractures. The results suggest that neither dissolution nor hydrogen-embrittlement processes occurred during stress-corrosion cracking in aluminium alloys. (Author).

Download or read book The Theory of Stress Corrosion Cracking in Alloys written by J. C. Scully and published by . This book was released on 1971 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: