Showing papers on "Stress corrosion cracking published in 1974"
TL;DR: In this article, a strain aging type of reversible hydrogen embrittlement has been demonstrated for a high strength aluminum alloy in a 3% NaCl environment, and the evidence is quite consistent with a mechanism of stress corrosion cracking (SCC) involving absorption of hydrogen leading to lattice dissolved hydrogen.
Abstract: A strain aging type of reversible hydrogen embrittlement has been demonstrated for a high strength aluminum alloy in a 3% NaCl environment. Permeation of hydrogen was related to SCC under cathodic polarization as well as anodic conditions. Internal friction and lattice parameter measurements relate directly to lattice dissolved hydrogen arising from the environment. It is concluded that the evidence is quite consistent with a mechanism of stress corrosion cracking (SCC) involving absorption of hydrogen leading to lattice dissolved hydrogen and embrittlement.
164 citations
01 Nov 1974-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, sustained load crack propagation of α-β titanium alloys is characterized by a mixture of microvoid coalescence with cleavage, usually on a plane 12 to 15 deg from the hep α phase with some cleavage.
Abstract: The fracture toughness and resistance to inert-environment sustained load crack propagation of α-β titanium alloys are usually reduced by increased hydrogen contents. The range of hydrogen contents over which either fracture toughness or threshold stress intensity for sustained load cracking was observed to decrease with hydrogen content is small (0 to 50 ppm) for Ti-6 Al-4 V, but further increases in hydrogen content can cause an increase in cracking rates. Sustained load crack propagation is characterized by a mixture of microvoid coalescence with cleavage, usually on a plane 12 to 15 deg from {0001} of the hep α phase with some {000l} cleavage. Cleavage apparently initiates ahead of the main crack front within a grains, usually near apparent α-β interfaces. Atmospheric moisture is inert with respect to sustained load cracking, that is, it does not cause stress corrosion cracking. Sustained load cracking was demonstrated in Ti-8 Al-1 Mo-1 V, Ti-6 Al-6 V-2 Sn, and several grades of Ti-6 Al-4 V.
104 citations
01 Jun 1974-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the fracture kinetics of Al-5.5 Zn-2.5 Mg alloys submersed in 3 pct NaCl-H2O solutions were varied by heat treatment.
Abstract: The fracture kinetics of Al-5.5 Zn-2.5 Mg alloys submersed in 3 pct NaCl-H2O solutions were varied by heat treatment. The steady state velocity, on a plot of velocity vs stress intensity, was compared with microstructure and it was found to be inversely proportional to the volume of MgZn2 in the grain boundary. This behavior suggests that grain boundary precipitates can act as sacrificial anodes to retard intergranular stress corrosion cracking.
55 citations
TL;DR: In this article, the authors described an instrumentation for obtaining current-time curves for new metal surfaces produced by fast fracture in electrolytes under potentiostatic conditions and showed that formation and growth of a salt film in the tip region would give a rapidly decaying current density moving away from the tip which would keep the tip sharp.
Abstract: Instrumentation is described for obtaining current-time curves for new metal surfaces produced by fast fracture in electrolytes under potentiostatic conditions. Measured anodic current densities for titanium specimens in acid solutions decayed about a million fold in a time of 10−4 to 103 seconds at which steady state was approached. Analysis of the experimental data indicate the actual initial current density for anodic dissolution is more than 10 A/cm2 in 3M HCl and may be orders of magnitude greater. Thus stress corrosion crack propagation by an anodic process in titanium cannot be ruled out. Formation of metal salt films would be predicted at high anodic current densities in cracks. Calculations show that formation and growth of a salt film in the tip region would give a rapidly decaying current density moving away from the tip which would keep the tip sharp. This phenomenon may be called the electrochemical knife.
43 citations
TL;DR: In this paper, the effect of strain rate on the stress corrosion cracking (SCC) of an austenitic stainless steel in MgCl2 solutions was investigated by using a constant strain rate method over the r...
Abstract: The effect of strain rate on the stress corrosion cracking (SCC) of an austenitic stainless steel in MgCl2 solutions has been investigated by using a constant strain rate method over the r...
35 citations
35 citations
01 Jul 1974
30 citations
Patent•
19 Aug 1974
TL;DR: In this article, the present invention relates to high chromium ferritic stainless steels and more particularly to improving their chloride stress corrosion cracking resistance and weldability, and is related to the work presented in this paper.
Abstract: The present invention relates to high chromium ferritic stainless steels and more particularly to improving their chloride stress corrosion cracking resistance and weldability.
23 citations
TL;DR: In this article, the effect of grain size, cold work, and sensitization has been studied on caustic stress corrosion cracking (SCC) experiments on Type 304, 304L, 316, 316L, and USS 18-18-2 stainless steels.
Abstract: Caustic stress corrosion cracking (SCC) experiments have been conducted on Type 304, 304L, 316, 316L, and USS 18-18-2 stainless steels. The environments used were deoxygenated 50% NaOH solution at 316 and 371 C (600 and 700 F), deoxygenated 10% NaOH solution at 316 C and atmospheric boiling [~149 C (300 F)] 50% NaOH. The effect of grain size, cold work, and sensitization has been studied. Metallurgical structures were examined with light microscopy and the accelerated Strauss test. Exposed specimens were studied with the light microscope and the fracture surfaces were studied with the scanning electron microscope (SEM). Variations in crack morphology were observed with caustic concentration and alloy content. Certain sensitization treatments were the only conditions identified in Type 304 as beneficial in increasing the high temperature caustic stress corrosion resistance.
20 citations
TL;DR: In this paper, the authors measured the susceptibility of iron to stress corrosion cracking (SCC) in nitrates, as a function of carbon, silicon, and germanium contents, and also for the binary alloys containing Ni, Cr, and Mo.
Abstract: Susceptibility of iron to stress corrosion cracking (SCC) in nitrates is measured as a function of carbon, silicon, and germanium contents, and also for the binary alloys containing Ni, Cr, and Mo. Effects of cold work and heat treatment are also studied. The results are related to crack-sensitive paths established by interstitial elements segregating along grain boundary regions.
18 citations
TL;DR: The fractography of all transgranular stress corrosion cracking (SCC) failures of the Zircaloys is generally similar and consists of areas of cleavage separated by regions of ductile teari...
Abstract: The fractography of all transgranular stress corrosion cracking (SCC) failures of the Zircaloys is generally similar and consists of areas of cleavage separated by regions of ductile teari...
TL;DR: In this paper, various stress corrosion tests have been carried out on a 3CrMo steel in ammonium acetate solution and intergranular cracking has occurred at both the molar and 0.1 molar levels.
Abstract: Various stress corrosion tests have been carried out on a 3CrMo steel in ammonium acetate solution. Intergranular cracking has occurred at both the molar and 0.1 molar levels. Other acetat...
01 Jul 1974
TL;DR: In this paper, the effects of welding and post-weld heat treatment on SCC susceptibility were investigated for a range of high strength steels, including conventional medium carbon, low alloy materials and low carbon, p recipients.
Abstract: High strength steels may suffer a form of stress corrosion cracking (SCC) due to hydrogen embritt lement, the hydrogen being liberated by a cathodic corrosion reaction. Most service media w i l l be expected to liberate hydrogen, and the problem affords a considerable drawback to the widespread use of high strength steels. For a number of reasons, fa i l ure may be particularly likely when welding is used for fabrication. Unless the structure is efficiently stress relieved, tensile stresses of yield or proof stress magnitude can remain in the vicinity of the weld, whi le even w i th stress relief, a we ld wi l l constitute a region of stress concentration. During the welding cycle, metallurgical changes may take place causing local microstructures that are particularly sensitive to SCC. The present investigation was initiated to clarify the situation, three particular objectives being identified, namely: 1. To define the relative SCC behavior of a range of high strength steels. 2. To assess the effects of welding and postweld heat treatment on SCC susceptibility. 3. To evaluate the general practical implications of the data obtained. A range ot steels was studied including both conventional medium carbon, low alloy materials and low carbon, p rec ip i ta t ion ha rden ing grades. SCC testing was based on T. G. GOOCH is Group Leader — Austenitic Group, The Welding institute, Abington, Cambridge, Great Britain. Paper was presented at the 55th AWS Annual Meeting held in Houston during May 6-10, 1974. linear elastic fracture mechanics pr inciples using precracked specimens. Testing was carried out in 3% sodium chloride solution as representative of the media causing SCC of high strength steels. Welds were prepared in the experimental alloys and the pre-existing crack located in various regions of the joint, whi le samples were also prepared using The Welding Institute weld thermal simulator to reproduce specific heat-affected zone (HAZ) microstructures. Susceptibil ity was defined in terms of the critical threshold stress intensity to cause cracking, the results obtained being related to material composition and microstructure w i th reference to different heat affected zone and weld metal areas. Fractographic examinat ion was carried out and susceptibility related to failure mechanism. From the results obtained it has been possible to derive a general understanding of the variables affecting weld SCC performance. Susceptibil ity is primarily dependent upon microstructure, and, for a given material, recommendations may be made regarding welding conditions and postweld heat treatment to obtain maximum SCC resistance. The presence of twinned martensite in particular should be avoided, since this ohase has a highly deleterious effect on SCC resistance. Provided postweld heat treatment similar to that specified for base metal is applied, HAZs and matching composit ion weld metals wi l l generally show SCC resistance similar to the base metal; wi thout such heat treatment, increased susceptibility must be anticipated. The presence of segregation and inclusions generally has little detrimental effect on weld metal SCC resistance, although segregation may be particularly significant in precipitat ion hardening systems. SCC failure may take place intergranularly, by cleavage, or by microvoid coalescence, intergranular failure being largely associated w i t h the presence of twinned martensite and high susceptibility. The results suggest that highest SCC resistance wi l l be obtained from low carbon, low alloy systems, since these are unlikely to suffer the development of deep corrosion pits wh ich may act to initiate SCC in service, and wi l l have high resistance to SCC by a cleavage mechanism. Attent ion has been further paid to the practical risk of SCC initiation in service, consideration being given to the effects of environment on SCC initiation and propagation. A preliminary correlation has been obtained between fracture mechanics data and the SCC behavior of uncracked, undressed welds. The information reported thus constitutes a rational basis for understanding the SCC behavior of welded joints. Although direct testing is still necessary to establish the behavior of a given joint in a particular environment, it is possible to maximize SCC resistance in advance by attention to relevant factors.
01 Jan 1974
TL;DR: The evidence available on the factors affecting the stress corrosion cracking (SCC) of the Zircaloys in iodine at elevated temperatures is summarized in this paper, where the authors show that cold work and irradiation hardening increase the susceptibility to SCC but other factors such as surface oxide conditions, crystallographic texture and residual stresses can also have appreciable effects.
Abstract: The evidence available on the factors affecting the stress corrosion cracking (SCC) of the Zircaloys in iodine at elevated temperatures is summarized. Cold work and irradiation hardening increase the susceptibility to SCC but other factors such as surface oxide conditions, crystallographic texture and residual stresses can also have appreciable effects. Evidence from fuel element testing together with the results of laboratory tests are now sufficient to permit the definite conclusion that fuel failures that occur after the sudden uprating of fuel elements can be caused by stress corrosion cracking. 48 references. (auth)
01 Jun 1974-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, a detailed study of rapid stress-corrosion-cracking in a 7075 aluminum alloy has allowed separation of the mechanical and chemical contributions, and a two-step crack growth mechanism was proposed combining a thermally activated electrochemical process and a discontinuous mechanical jumping process.
Abstract: A detailed study of rapid stress-corrosion-cracking (SCC) in a 7075 aluminum alloy has allowed separation of the mechanical and chemical contributions. This was accomplished by combining scanning electron microscopy, stress-wave emission and crack growth rate observations as a function of test temperature. These established an activation energy of 11.2 kcal/mol, a stress-intensity squared dependence of crack growth, and a range of 20 to 80 pct dimpled rupture on the fracture surfaces. Thus a two-step crack growth mechanism is proposed combining a thermally activated electrochemical process and a discontinuous mechanical jumping process.
TL;DR: In this paper, the susceptibility of this alloy to stress corrosion cracking (SCC) in dilute saline solution is dependent on the hydrogen content of the material and the removal of hydrogen results in increasing K ie and K isec until at about 5 ppm level the material shows immunity to SCC.
01 Jan 1974
TL;DR: In this article, stress-corrosion cracking (SCC) was studied in four grades of 99+% dense MgO with the major variables grain size and purity.
Abstract: Stress-corrosion cracking (SCC) was studied in four grades of 99+% dense MgO with the major variables grain size and purity. Testing consisted of four-point bend and static fatigue tests in H2O, DMF, and DMSO-DMF solutions. In an H2O environment the highest purity material gave the slowest strength loss. SCC in low purity grades was judged to be controlled by a chemical interaction of OH- with a (CaNaSiAl)Ox or LiF grain boundary phase. The highest purity grade tested (99.98+% MgO) may not have a discrete grain boundary phase, so the low corrosion rate and high static fatigue limit of ≃0.83σD may be characteristic of an intrinsic process. The possibility exists that this was caused by a shift in mechanism, but a passive film model consistent with the data is proposed. When H2O is present, chemical corrosion is believed to have faster SCC kinetics than possible competing processes. This was demonstrated for the second purest (99.92+% MgO) specimens. Testing in DMSO + 10% DMF and DMF gave a sufficient separation of the data to conclude that the Rebinder effect was also operative. Thus, under certain conditions, SCC can result from a dislocation model of crack nucleation. Stress intensity factors, K, were calculated based on the conclusion that the Griffith model was operative. The calculated K-V (velocity) diagram was thought to be qualitatively correct in showing that the second purest sintered grade of MgO had the best overall behavior in terms of dry strength and static fatigue in a H2O environment. However, the static fatigue performance and nearly identical KISCC for the highest purity material suggested that the high purity hot pressed grade showed the most promise from a materials development viewpoint.
01 Jan 1974
TL;DR: In the recent literature in various fields of research, an interest has developed in several aspects of mass transport to the tips of Griffith-type cracks by diffusional processes as mentioned in this paper, and diffusion of chemically active species to crack tips can also control stress corrosion cracking.
Abstract: In the recent literature in various fields of research, an interest has developed in several aspects of mass transport to the tips of Griffith-type cracks by diffusional processes. This phenomenon is, for example, of importance to creep rupture behaviour where fracture may result from the growth of grain boundary cracks by diffusion of vacancies to the crack tip. Similar growth processes can also be responsible for static fatigue observed in many ceramic materials. Diffusion of chemically active species to crack tips can also control stress corrosion cracking.
TL;DR: The applicability of austenitic stainless steel for anchoring farade panels has been studied in this paper, where it is shown that under certain conditions the possibility of stress corrosion in stainless steel fixings must be taken into account.
Abstract: The applicability of austenitic stainless steel for anchoring farade panels has been studied. It is shown that under certain conditions the possibility of stress corrosion in austenitic stainless steel fixings must be taken into account. Stress corrosion will occur only at a particular combination of stress, chloride concentration and temperature, and in practice the probability of serious damage has always been low. On the basis of ‘low-temperature’ stress corrosion tests in the laboratory, it has been decided in the Netherlands to allow the use of austenitic stainless steel for facade anchors only in conditions where the maximum anchor temperature does not rise above 50°c.Dutch views on the applicability of austenitic steel as anchor material for facade panels are discussed.
TL;DR: In this article, a number of failures due to stress corrosion cracking have been discovered, which has been traced to the alkaline environment round the pipe produced by the cathodic protecion process, combined with subsequent concentration by evaporation.
Abstract: Inadequate design or construction of certain district heating distribution systems has led to severe corrosion problems. These systems were then cathodically protected by means of impressed current installations, and the frequency of leaks was thereby reduced. However, following this, a number of failures due to stress corrosion cracking have been discovered. This has been traced to the alkaline environment round the pipe produced by the cathodic protecion process, combined with subsequent concentration by evaporation, the potential of the pipe then being in the range known to promote caustic cracking when residual stresses are present in the pipe. The only possible solutions to the problem for existing pipelines are either to remove the cathodic protection and revert to the likelihood of general corrosion problems, or to control the applied current so that the pipeline is kept out of the potential range known to promote stress corrosion. In practice this is difficult to achieve and may result in...
TL;DR: In this article, the authors investigated the environmental fatigue crack propagation resistance in four commercial titanium alloys of medium strength and found that the material with the highest elastic moduli, Ti-5Al-2.5Sn, had the best crack propagation resilience in the absence of stress corrosion.
01 Jan 1974
TL;DR: Corrosion of steam generator tubing has been observed in all but three PWRs that have been in operation for more than one year as discussed by the authors. But, the history of this experience with both stainless steel and Inconel-600 tubing is reviewed.
Abstract: Corrosion of steam generator tubing has been observed in all but three PWR's that have been in operation for more than one year. The history of this experience with both stainless steel and Inconel-600 tubing is reviewed. Both intergranular stress corrosion cracking and localized, transgranular wastage have been observed with Inconel-600 tubing. The wastage can be attributed to a localized concentration, or ''hideout'' of phosphates in limited flow areas. A model is proposed for this wastage phenomenon which is consistent with operating experience. 33 references. (auth)
TL;DR: In this article, three deteriorated structures exposed to different environmental conditions in Egypt and a non-deteriorated structure have been inspected, and microscopic examination of reinforcing steel samples from the different constructions revealed the occurrence of pitting corrosion in the reinforcement of a building exposed to a marine atmosphere, local and general attack in the reinforced of a Filtration Building for the Domestic Water Project and stress corrosion cracking in the horizontal reinforcement of some concrete columns of the building made of Portland blast furnace slag cement.
Abstract: Three deteriorated structures exposed to different environmental conditions in Egypt and a non-deteriorated structure have been inspected. Visual and microscopic examination of reinforcing steel samples from the different constructions revealed the occurrence of pitting corrosion in the reinforcement of a building exposed to a marine atmosphere, local and general attack in the reinforcement of a Filtration Building for the Domestic Water Project and stress corrosion cracking in the horizontal reinforcement of some concrete columns of a building made of Portland blast furnace slag cement. It has been found that the type of corrosion is mainly determined by the type of aggressive ions present in the concrete and ta a lesser extent by the microstructure of steel. Examination of the non-deteriorated structure led to the conclusion that low concentrations of aggressive ions in, and high alkalinity of, the concrete, relatively low C and S contents of the reinforcement and a non-aggressive surrounding at...
TL;DR: In this article, a round robin stress corrosion testing program was carried out at seven divisions of Rockwell International to evaluate and compare techniques for assessing stress corrosion susceptibility; the most important experimental parameters were carefully controlled and maintained as uniform as possible.
Abstract: A round robin stress corrosion testing program was carried out at seven divisions of Rockwell International to evaluate and compare techniques for assessing stress corrosion susceptibility. Tests were conducted on the recently developed 7049 aluminum alloy, after it had been heat treated to the T6 and T73 tempers, as well as to an underaged and an overaged temper. The most important experimental parameters were carefully controlled and maintained as uniform as possible. The tests tended to yield similar rankings of the four tempers. They differed mainly in severity and sensitivity to changes in heat treatment and stress level. Results of the conventional time to failure tests indicated that susceptibility to SCC decreased regularly with aging. Under the most severe test conditions, failures were observed in the most highly overaged temper at an applied stress of 35% yield strength. A hypothetical combination of tensile type or interference fit specimens, alternate immersion or salt spray exposure...
TL;DR: In this article, a general decrease in cracking susceptibility has been observed from methyl to butyl amine, and the cracking pattern changes from intergranular to transgranular, indicating the potential range of maximum susceptibility also shifts towards more negative values with the substitution of higher amines.
Abstract: Stress corrosion cracking of α-brass in the annealed and cold worked states has been investigated under potentiostatic anodic and cathodic polarisation in Mattsson type solutions in which ammonia has been substituted with methyl, ethyl and butyl amines. A general decrease in cracking susceptibility has been observed from methyl to butyl amine, and the cracking pattern changes from intergranular to transgranular.The potential range of maximum susceptibility also shifts towards more negative values with the substitution of higher amines. These observations have been explained on the basis of active anodic and cathodic sites influenced by adsorption and polarisation processes.