Stress corrosion cracking of several high strength ferrous and nickel alloys

NASA Technical Reports Server (NTRS)

Nelson, E. E.

1971-01-01

The stress corrosion cracking resistance of several high strength ferrous and nickel base alloys has been determined in a sodium chloride solution. Results indicate that under these test conditions Multiphase MP35N, Unitemp L605, Inconel 718, Carpenter 20Cb and 20Cb-3 are highly resistant to stress corrosion cracking. AISI 410 and 431 stainless steels, 18 Ni maraging steel (250 grade) and AISI 4130 steel are susceptible to stress corrosion cracking under some conditions.

Stress corrosion cracking evaluation of precipitation-hardening stainless steel

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1970-01-01

Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

Monitoring the corrosion process of reinforced concrete using BOTDA and FBG sensors.

PubMed

Mao, Jianghong; Chen, Jiayun; Cui, Lei; Jin, Weiliang; Xu, Chen; He, Yong

2015-04-15

Expansion and cracking induced by the corrosion of reinforcement concrete is the major factor in the failure of concrete durability. Therefore, monitoring of concrete cracking is critical for evaluating the safety of concrete structures. In this paper, we introduce a novel monitoring method combining Brillouin optical time domain analysis (BOTDA) and fiber Bragg grating (FBG), based on mechanical principles of concrete expansion cracking. BOTDA monitors concrete expansion and crack width, while FBG identifies the time and position of cracking. A water-pressure loading simulation test was carried out to determine the relationship between fiber strain, concrete expansion and crack width. An electrical accelerated corrosion test was also conducted to evaluate the ability of this novel sensor to monitor concrete cracking under practical conditions.

A Monitoring Method Based on FBG for Concrete Corrosion Cracking

PubMed Central

Mao, Jianghong; Xu, Fangyuan; Gao, Qian; Liu, Shenglin; Jin, Weiliang; Xu, Yidong

2016-01-01

Corrosion cracking of reinforced concrete caused by chloride salt is one of the main determinants of structure durability. Monitoring the entire process of concrete corrosion cracking is critical for assessing the remaining life of the structure and determining if maintenance is needed. Fiber Bragg Grating (FBG) sensing technology is extensively developed in photoelectric monitoring technology and has been used on many projects. FBG can detect the quasi-distribution of strain and temperature under corrosive environments, and thus it is suitable for monitoring reinforced concrete cracking. According to the mechanical principle that corrosion expansion is responsible for the reinforced concrete cracking, a package design of reinforced concrete cracking sensors based on FBG was proposed and investigated in this study. The corresponding relationship between the grating wavelength and strain was calibrated by an equal strength beam test. The effectiveness of the proposed method was verified by an electrically accelerated corrosion experiment. The fiber grating sensing technology was able to track the corrosion expansion and corrosion cracking in real time and provided data to inform decision-making for the maintenance and management of the engineering structure. PMID:27428972

A Monitoring Method Based on FBG for Concrete Corrosion Cracking.

PubMed

Mao, Jianghong; Xu, Fangyuan; Gao, Qian; Liu, Shenglin; Jin, Weiliang; Xu, Yidong

2016-07-14

Corrosion cracking of reinforced concrete caused by chloride salt is one of the main determinants of structure durability. Monitoring the entire process of concrete corrosion cracking is critical for assessing the remaining life of the structure and determining if maintenance is needed. Fiber Bragg Grating (FBG) sensing technology is extensively developed in photoelectric monitoring technology and has been used on many projects. FBG can detect the quasi-distribution of strain and temperature under corrosive environments, and thus it is suitable for monitoring reinforced concrete cracking. According to the mechanical principle that corrosion expansion is responsible for the reinforced concrete cracking, a package design of reinforced concrete cracking sensors based on FBG was proposed and investigated in this study. The corresponding relationship between the grating wavelength and strain was calibrated by an equal strength beam test. The effectiveness of the proposed method was verified by an electrically accelerated corrosion experiment. The fiber grating sensing technology was able to track the corrosion expansion and corrosion cracking in real time and provided data to inform decision-making for the maintenance and management of the engineering structure.

Failure Pressure and Leak Rate of Steam Generator Tubes With Stress Corrosion Cracks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majumdar, S.; Kasza, K.; Park, J.Y.

2002-07-01

This paper illustrates the use of an 'equivalent rectangular crack' approach to predict leak rates through laboratory generated stress corrosion cracks. A comparison between predicted and observed test data on rupture and leak rate from laboratory generated stress corrosion cracks are provided. Specimen flaws were sized by post-test fractography in addition to pre-test advanced eddy current technique. The test failure pressures and leak rates are shown to be closer to those predicted on the basis of fractography than on NDE. However, the predictions based on NDE results are encouraging, particularly because they have the potential to determine a more detailedmore » geometry of ligamentous cracks from which more accurate predictions of failure pressure and leak rate can be made in the future. (authors)« less

Strain rate effects in stress corrosion cracking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parkins, R.N.

Slow strain rate testing (SSRT) was initially developed as a rapid, ad hoc laboratory method for assessing the propensity for metals an environments to promote stress corrosion cracking. It is now clear, however, that there are good theoretical reasons why strain rate, as opposed to stress per se, will often be the controlling parameter in determining whether or not cracks are nucleated and, if so, are propagated. The synergistic effects of the time dependence of corrosion-related reactions and microplastic strain provide the basis for mechanistic understanding of stress corrosion cracking in high-pressure pipelines and other structures. However, while this maymore » be readily comprehended in the context of laboratory slow strain tests, its extension to service situations may be less apparent. Laboratory work involving realistic stressing conditions, including low-frequency cyclic loading, shows that strain or creep rates give good correlation with thresholds for cracking and with crack growth kinetics.« less

Monitoring the Corrosion Process of Reinforced Concrete Using BOTDA and FBG Sensors

PubMed Central

Mao, Jianghong; Chen, Jiayun; Cui, Lei; Jin, Weiliang; Xu, Chen; He, Yong

2015-01-01

Expansion and cracking induced by the corrosion of reinforcement concrete is the major factor in the failure of concrete durability. Therefore, monitoring of concrete cracking is critical for evaluating the safety of concrete structures. In this paper, we introduce a novel monitoring method combining Brillouin optical time domain analysis (BOTDA) and fiber Bragg grating (FBG), based on mechanical principles of concrete expansion cracking. BOTDA monitors concrete expansion and crack width, while FBG identifies the time and position of cracking. A water-pressure loading simulation test was carried out to determine the relationship between fiber strain, concrete expansion and crack width. An electrical accelerated corrosion test was also conducted to evaluate the ability of this novel sensor to monitor concrete cracking under practical conditions. PMID:25884790

Caustic stress corrosion tests for the LLTR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Indig, M.E.

1976-05-01

A series of tests have been performed in order to determine the effects of the caustic resulting from the Na/H/sub 2/O reaction on the materials used in the LLTR-MSG series of testing. Stainless steel, 2 /sup 1///sub 4/ Cr--1 Mo and carbon steel have been evaluated. Stress corrosion cracking susceptibility and general corrosion are reported. Over the range of temperature, caustic concentration and heating rate tested the stainless steel stressed to 90% of yield or above suffered cracking. Whereas, the 2-/sup 1///sub 4/ Cr--1 Mo and carbon steel were not cracked.

Influence of precracked specimen configuration and starting stress intensity on the stress corrosion cracking of 4340 steel

NASA Technical Reports Server (NTRS)

Lisagor, W. B.

1984-01-01

Since the pioneer work of Brown (1966), precracked specimens and related fracture mechanics analyses have been extensively used to study stress corrosion cracking. Certain questions arose in connection with initial attempts to prepare standardized recommended practices by ASTM Committee G-1 on Corrosion of Metals. These questions were related to adequacy of test control as it pertains to acceptable limits of variability, and to validity of expressions for stress intensity and crack-surface displacements for both specimen configurations. An interlaboratory test program, was, therefore, planned with the objective to examine the validity of KIscc testing for selected specimen configurations, materials,and environmental systems. The results reported in the present paper include details of a single laboratory test program. The program was conducted to determine if the threshold value of stress intensity for onset and arrest of stress corrosion cracking was independent for the two specimen configurations examined.

Prediction of corrosion fatigue crack initiation behavior of A7N01P-T4 aluminum alloy welded joints

NASA Astrophysics Data System (ADS)

An, J.; Chen, J.; Gou, G.; Chen, H.; Wang, W.

2017-07-01

Through investigating the corrosion fatigue crack initiation behavior of A7N01P-T4 aluminum alloy welded joints in 3.5 wt.% NaCl solution, corrosion fatigue crack initiation life is formulated as Ni = 6.97 × 1012[Δσeqv1.739 - 491.739]-2 and the mechanism of corrosion fatigue crack initiation is proposed. SEM and TEM tests revealed that several corrosion fatigue cracks formed asynchronously and the first crack does not necessarily develop into the leading crack. The uneven reticular dislocations produced by fatigue loading are prone to piling up and tangling near the grain boundaries or the second phases and form the “high dislocation-density region” (HDDR), which acts as an anode in microbatteries and dissolved to form small crack. Thus the etching pits, HDDR near the grain boundaries and second phases are confirmed as the main causes inducing the initiation of fatigue crack.

Origins of Negative Strain Rate Dependence of Stress Corrosion Cracking Initiation in Alloy 690, and Intergranular Crack Formation in Thermally Treated Alloy 690

NASA Astrophysics Data System (ADS)

Kim, Young Suk; Kim, Sung Soo

2016-09-01

We show that enhanced stress corrosion cracking (SCC) initiation in cold-rolled Alloy 690 with decreasing strain rate is related to the rate of short-range ordering (SRO) but not to the time-dependent corrosion process. Evidence for SRO is provided by aging tests on cold-rolled Alloy 690 at 623 K and 693 K (350 °C and 420 °C), respectively, which demonstrate its enhanced lattice contraction and hardness increase with aging temperature and time, respectively. Secondary intergranular cracks formed only in thermally treated and cold-rolled Alloy 690 during SCC tests, which are not SCC cracks, are caused by its lattice contraction by SRO before SCC tests but not by the orientation effect.

Effect of Stress Ratio and Loading Frequency on the Corrosion Fatigue Behavior of Smooth Steel Wire in Different Solutions

PubMed Central

Wang, Songquan; Zhang, Dekun; Hu, Ningning; Zhang, Jialu

2016-01-01

In this work, the effects of loading condition and corrosion solution on the corrosion fatigue behavior of smooth steel wire were discussed. The results of polarization curves and weight loss curves showed that the corrosion of steel wire in acid solution was more severe than that in neutral and alkaline solutions. With the extension of immersion time in acid solution, the cathodic reaction of steel wire gradually changed from the reduction of hydrogen ion to the reduction of oxygen, but was always the reduction of hydrogen ion in neutral and alkaline solutions. The corrosion kinetic parameters and equivalent circuits of steel wires were also obtained by simulating the Nyquist diagrams. In corrosion fatigue test, the effect of stress ratio and loading frequency on the crack initiation mechanism was emphasized. The strong corrosivity of acid solution could accelerate the nucleation of crack tip. The initiation mechanism of crack under different conditions was summarized according to the side and fracture surface morphologies. For the crack initiation mechanism of anodic dissolution, the stronger the corrosivity of solution was, the more easily the fatigue crack source formed, while, for the crack initiation mechanism of deformation activation, the lower stress ratio and higher frequency would accelerate the generation of corrosion fatigue crack source. PMID:28773869

The effects of pitting on fatigue crack nucleation in 7075-T6 aluminum alloy

NASA Technical Reports Server (NTRS)

Ma, LI; Hoeppner, David W.

1994-01-01

A high-strength aluminum alloy, 7075-T6, was studied to quantitatively evaluate chemical pitting effects of its corrosion fatigue life. The study focused on pit nucleation, pit growth, and fatigue crack nucleation. Pitting corrosion fatigue experiments were conducted in 3.5 percent NaCl aqueous solution under constant amplitude sinusoidal loading at two frequencies, 5 and 20 Hz. Smooth and unnotched specimens were used in this investigation. A video recording system was developed to allow in situ observation of the surface changes of the specimens during testing. The results indicated that pitting corrosion considerably reduces the fatigue strength by accelerating fatigue crack nucleation. A metallographic examination was conducted on the specimens to evaluate the nature of corrosion pits. First, the actual shapes of the corrosion pits were evaluated by cross-sectioning the pits. Secondly, the relation between corrosion pits and microstructure was also investigated. Finally, the possibility of another corrosion mechanism that might be involved in pitting was explored in this investigation. The fractography of the tested specimens showed that corner corrosion pits were responsible for fatigue crack nucleation in the material due to the associated stress concentration. The pits exhibited variance of morphology. Fatigue life for the experimental conditions appeared to be strongly dependent on pitting kinetics and the crack nucleation stage.

The effect of heat treatment and test parameters on the aqueous stress corrosion cracking of D6AC steel

NASA Technical Reports Server (NTRS)

Gilbreath, W. P.; Adamson, M. J.

1974-01-01

The crack growth behavior of D6AC steel as a function of stress intensity, stress and corrosion history and test technique, under sustained load in natural seawater, 3.3 percent NaCl solution, distilled water, and high humidity air was investigated. Reported investigations of D6AC were considered with emphasis on thermal treatment, specimen configuration, fracture toughness, crack-growth rates, initiation period, threshold, and the extension of corrosion fatigue data to sustained load conditions. Stress history effects were found to be most important in that they controlled incubation period, initial crack growth rates, and apparent threshold.

Seacoast stress corrosion cracking of aluminum alloys

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1981-01-01

The stress corrosion cracking resistance of high strength, wrought aluminum alloys in a seacoast atmosphere was investigated and the results were compared with those obtained in laboratory tests. Round tensile specimens taken from the short transverse grain direction of aluminum plate and stressed up to 100 percent of their yield strengths were exposed to the seacoast and to alternate immersion in salt water and synthetic seawater. Maximum exposure periods of one year at the seacoast, 0.3 or 0.7 of a month for alternate immersion in salt water, and three months for synthetic seawater were indicated for aluminum alloys to avoid false indications of stress corrosion cracking failure resulting from pitting. Correlation of the results was very good among the three test media using the selected exposure periods. It is concluded that either of the laboratory test media is suitable for evaluating the stress corrosion cracking performance of aluminum alloys in seacoast atmosphere.

Detection of stress corrosion cracking and general corrosion of mild steel in simulated defense nuclear waste solutions using electrochemical noise analysis

NASA Astrophysics Data System (ADS)

Edgemon, G. L.; Danielson, M. J.; Bell, G. E. C.

1997-06-01

Underground waste tanks fabricated from mild steel store more than 253 million liters of high level radioactive waste from 50 years of weapons production at the Hanford Site. The probable modes of corrosion failures are reported as nitrate stress corrosion cracking and pitting. In an effort to develop a waste tank corrosion monitoring system, laboratory tests were conducted to characterize electrochemical noise data for both uniform and localized corrosion of mild steel and other materials in simulated waste environments. The simulated waste solutions were primarily composed of ammonium nitrate or sodium nitrate and were held at approximately 97°C. The electrochemical noise of freely corroding specimens was monitored, recorded and analyzed for periods ranging between 10 and 500 h. At the end of each test period, the specimens were examined to correlate electrochemical noise data with corrosion damage. Data characteristic of uniform corrosion and stress corrosion cracking are presented.

Effects of environmental variables on the crack initiation stages of corrosion fatigue of high strength aluminum alloys

NASA Technical Reports Server (NTRS)

Poteat, L. E.

1981-01-01

Fatigue initiation in six aluminum alloys used in the aircraft industry was investigated. Cyclic loading superimposed on a constant stress was alternated with atmospheric corrosion. Tests made at different stress levels revealed that a residual stress as low as 39% of the yield strength caused stress corrosion cracking in some of the alloys. An atmospheric corrosion rate meter developed to measure the corrosivity of the atmosphere is described. An easily duplicated hole in the square test specimen with a self-induced residual stress was developed.

The effect of cathodic polarization on the corrosion fatigue behavior of a precipitation hardened aluminum alloy

NASA Astrophysics Data System (ADS)

Smith, E. F.; Duquette, D. J.

1986-02-01

Fatigue experiments were conducted on polycrystalline and monocrystalline samples of a high purity Al, 5.5 wt pct Zn, 2.5 wt pct Mg, 1.5 wt pct Cu alloy in the peak-hardened heat treatment condition. These experiments were conducted in dry laboratory air and in 0.5 N NaCl solutions at the corrosion potential and at applied potentials cathodic to the corrosion potential. It has been shown that saline solutions severely reduce the fatigue resistance of the alloy, resulting in considerable amounts of intergranular crack initiation and propagation under freely corroding conditions for polycrystalline samples. Applied cathodic potentials resulted in still larger decreases in fatigue resistance and, for poly crystals, increases in the degree of transgranular crack initiation and propagation. Increasing amounts of intergranular cracking were observed when applied cyclic stresses were reduced (longer test times). The characteristics of cracking, combined with results obtained on tensile tests of deformed and hydrogen charged samples, suggest that environmental cracking of these alloys is associated with a form of hydrogen embrittlement of the process zones of growing cracks. Further, it is suggested that stress corrosion cracking and corrosion fatigue of these alloys occurs by essentially the same mechanism, but that the often observed transgranular cracking under cyclic loading conditions occurs due to enhanced hydrogen transport and/or concentrations associated with mobile dislocations at growing crack tips.

Use of electrochemical potential noise to detect initiation and propagation of stress corrosion cracks in a 17-4 PH steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonzalez-Rodriguez, J.G.; Salinas-Bravo, V.M.; Garcia-Ochoa, E.

1997-09-01

Corrosion potential transients were associated with nucleation and propagation of stress corrosion cracks in a 17-4 precipitation-hardenable (PH) martensitic stainless steel (SS) during slow strain rate tests (SSRT) at 90 C in deaerated sodium chloride (NaCl) solutions, Test solutions included 20 wt% NaCl at pH 3 and 7, similar to normal and faulted steam turbine environments, respectively. Time series were analyzed using the fast Fourier transform method. At the beginning of straining, the consistent noise behavior was perturbed with small potential transients, probably associated with rupture of the surface oxide layer. After yielding, these transients increased in intensity. At maximummore » load, the transients were still higher in intensity and frequency. These potential transients were related to crack nucleation and propagation. When the steel did not fail by stress corrosion cracking (SCC), such transients were found only at the beginning of the test. The power spectra showed some differences in all cases in roll-off slope and voltage magnitude, but these were not reliable tools to monitor the initiation and propagation of stress corrosion cracks.« less

Stress Corrosion Cracking of Pipeline Steels in Fuel Grade Ethanol and Blends - Study to Evaluate Alternate Standard Tests and Phenomenological Understanding of SCC

DOT National Transportation Integrated Search

2011-10-30

Main aim of this project was to evaluate alternate standard test methods for stress corrosion cracking (SCC) and compare them with the results from slow strain rate test (SSRT) results under equivalent environmental conditions. Other important aim of...

EFFECTS OF CHEMISTRY AND OTHER VARIABLES ON CORROSION AND STRESS CORROSION CRACKING IN HANFORD DOUBLE SHELL TANKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

BROWN MH

2008-11-13

Laboratory testing was performed to develop a comprehensive understanding of the corrosivity of the tank wastes stored in Double-Shell Tanks using simulants primarily from Tanks 241-AP-105, 241-SY-103 and 241-AW-105. Additional tests were conducted using simulants of the waste stored in 241-AZ-102, 241-SY-101, 241-AN-107, and 241-AY-101. This test program placed particular emphasis on defining the range of tank waste chemistries that do not induce the onset of localized forms of corrosion, particularly pitting and stress corrosion cracking. This document summarizes the key findings of the research program.

Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, J C

2003-04-15

DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption inmore » crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with temperature controlled cells for potentiostatic and potentiodynamic testing (Figure 2).« less

Stress corrosion cracking evaluation of martensitic precipitation hardening stainless steels

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1980-01-01

The resistance of the martensitic precipitation hardening stainless steels PH13-8Mo, 15-5PH, and 17-4PH to stress corrosion cracking was investigated. Round tensile and c-ring type specimens taken from several heats of the three alloys were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, to salt spray, and to a seacoast environment. The results indicate that 15-5PH is highly resistant to stress corrosion cracking in conditions H1000 and H1050 and is moderately resistant in condition H900. The stress corrosion cracking resistance of PH13-8Mo and 17-4PH stainless steels in conditions H1000 and H1050 was sensitive to mill heats and ranged from low to high among the several heats included in the tests. Based on a comparison with data from seacoast environmental tests, it is apparent that alternate immersion in 3.5 percent salt water is not a suitable medium for accelerated stress corrosion testing of these pH stainless steels.

Determining cyclic corrosion cracking resistance for titanium alloys with allowance for electrochemical conditions at the fatigue corrosion crack tip

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panasyuk, V.V.; Ratich, L.V.; Petranyuk, I.Ya.

1994-08-01

Published data are examined on how various factors affect fatigue crack growth rates. Basic diagrams have been constructed for the cyclic cracking resistance in Ti-6Al-4V and Ti-6Al-2Sn alloys in air, distilled water, and 3.5% NaCl for use in working-life calculations. Appropriate heat treatment can produce two microstructures in a titanium alloy, one of which has the largest cyclic cracking resistance, while in the second, the cracks grow at the lowest rate. The cyclic corrosion cracking resistance for a titanium alloy should be determined in relation to the state of stress and strain and to the electrochemical conditions at the corrosionmore » fatigue crack tip, while the variations in fatigue crack growth rate for a given stress intensity factor in a corrosive medium are due to differing electrochemical conditions at the crack tip during the testing on different specimens. Basic diagrams can be derived for titanium alloys by using a physically sound methodology developed previously for steels, which is based on invariant diagrams for cyclic cracking resistance in air and in the corresponding medium, which can be constructed in relation to extremal working and electrochemical conditions at corrosion-fatigue crack tips.« less

Development of an Improved Crack Propagation Model for Corrosion-Induced Cover Cracking in RC Structures

NASA Astrophysics Data System (ADS)

Hilyati, S.; Nizam, Z. M.; Zurisman, M. A. A.; Azhar, A. T. S.

2017-06-01

During the last two decades, reinforced concrete (RC) has been extensively used in most of the world as one of the common construction material due to its advantages and durability. However, RC structures exposed to marine environments are subjected to chloride attack. Chlorides from seawater penetrate into RC structures are not only causing severe corrosion problems but also affect the durability and serviceability of such structures. This paper investigates the influence of transverse reinforcement and spacing of reinforcing bars on concrete cover cracking of two-way RC slab specimens using accelerated corrosion tests. The experimental program involved the testing of four RC slab specimens and was generally designed to observe the crack width and the time of crack to propagate. An improved model for predicting the timing of crack propagation based on the experimental data was then developed.

Stress-corrosion behavior of aluminum-lithium alloys in aqueous salt environments

NASA Technical Reports Server (NTRS)

Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

1984-01-01

The stress corrosion susceptibility of two powder metallurgy (P/M) alloys, Al-Li-Cu and Al-Li-Cu-Mg; two mechanically attrited (M/A) alloys, Al-Li-Cu and Al-Li-Mg; and two wrought, ingot alloys, X-2020 and AA7475, are compared. Time-dependent fracture in an aqueous sodium chloride environment under alternate immersion condition was found to vary significantly between alloys. The stress corrosion behavior of the two powder metallurgy processed alloys was studied in detail under conditions of crack initiation, static crack growth, and fatigue crack growth. A variety of stress corrosion tests were performed including smooth surface, time-to-failure tests; potentiostatic tests on smooth surfaces exposed to constant applied strain rates; and fracture mechanics-type tests under static and cyclic loads. Both alloys show surface pitting and subsequent intergranular corrosion. Pitting is more severe in the magnesium-bearing alloy and is associated with stringer particles strung along the extrusion direction as a result of P/M processing.

Stress-corrosion behavior of aluminum-lithium alloys in aqueous environments

NASA Technical Reports Server (NTRS)

Pizzo, P. P.; Galvin, R. P.; Nelson, H. G.

1983-01-01

The stress corrosion susceptibility of two powder metallurgy (P/M) alloys, Al-Li-Cu and Al-Li-Cu-Mg two mechanically attrited (M/A) alloys, Al-Li-Cu and Al-Li-Mg; and two wrought, ingot alloys, X-2020 and AA7475, are compared. Time-dependent fracture in an aqueous sodium chloride environment under alternate immersion condition was found to vary significantly between alloys. The stress corrosion behavior of the two powder metallurgy processed alloys was studied in detail under conditions of crack initiation, static crack growth, and fatigue crack growth. A variety of stress corrosion tests were performed including smooth surface, time-to-failure tests; potentiostatic tests on smooth surfaces exposed to constant applied strain rates; and fracture mechanics-type tests under static and cyclic loads. Both alloys show surface pitting and subsequent intergranular corrosion. Pitting is more severe in the magnesium-bearing alloy and is associated with stringer particles strung along the extrusion direction as a result of P/M processing.

Ultrasonic Corrosion Fatigue Behavior of High Strength Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Ebara, R.; Yamaguchi, Y.; Kanei, D.; Yamamoto, Y.

Ultrasonic corrosion fatigue tests were conducted for high strength austenitic stainless steels such as YUS270 and SUS304N2 in 3%NaCl aqueous solution. The reduction of giga-cycle corrosion fatigue strength of YUS270 and SUS304N2 was not observed at all, while the reduction of corrosion fatigue life was observed at higher stress amplitude. Corrosion pit was observed on corrosion fatigue crack initiation area. Striation was predominantly observed on crack propagation area in air and in 3% NaCl aqueous solution. The reduction of corrosion fatigue strength of high strength austenitic stainless steels such as YUS270 and SUS304N2 is due to the corrosion pit formation at corrosion fatigue crack initiation area. It can be concluded that the higher the ultimate tensile strength of austenitic stainless steels the higher the giga-cycle corrosion fatigue strength in 3%NaCl aqueous solution is.

Data-Science Analysis of the Macro-scale Features Governing the Corrosion to Crack Transition in AA7050-T7451

NASA Astrophysics Data System (ADS)

Co, Noelle Easter C.; Brown, Donald E.; Burns, James T.

2018-05-01

This study applies data science approaches (random forest and logistic regression) to determine the extent to which macro-scale corrosion damage features govern the crack formation behavior in AA7050-T7451. Each corrosion morphology has a set of corresponding predictor variables (pit depth, volume, area, diameter, pit density, total fissure length, surface roughness metrics, etc.) describing the shape of the corrosion damage. The values of the predictor variables are obtained from white light interferometry, x-ray tomography, and scanning electron microscope imaging of the corrosion damage. A permutation test is employed to assess the significance of the logistic and random forest model predictions. Results indicate minimal relationship between the macro-scale corrosion feature predictor variables and fatigue crack initiation. These findings suggest that the macro-scale corrosion features and their interactions do not solely govern the crack formation behavior. While these results do not imply that the macro-features have no impact, they do suggest that additional parameters must be considered to rigorously inform the crack formation location.

Electrochemical Interpretation of a Stress Corrosion Cracking of Thermally Treated Ni base Alloys in a Lead Contaminated Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, Seong Sik; Lim, Yun Soo; Kim, Hong Pyo

2007-08-20

Since the PbSCC(Lead stress corrosion cracking) of alloy 600 tubing materials was reported by Copson and Dean in 1965, the effect of lead on a corrosion film and cracking morphology have been continually debated. An electrochemical interaction of lead with the alloying elements of SG tubings was studied and the corrosion products were analyzed. It was found that lead enhanced the anodic dissolution of alloy 600 and alloy 690 in the electrochemical test. The lead preferentially dissolved the Cr from the corrosion film of alloy 600 and alloy 690 in alkaline water. The lead ion seemed to penetrate into themore » TG crack tip and react with the corrosion film. A selective Cr depletion was observed to weaken the stability of the passive film on the alloys. Whereas passivity of Ni became stable in lead containing solution, Cr and Fe passivity became unstable.« less

Stress Corrosion Cracking Behavior of Hardening-Treated 13Cr Stainless Steel

NASA Astrophysics Data System (ADS)

Niu, Li-Bin; Ishitake, Hisamitsu; Izumi, Sakae; Shiokawa, Kunio; Yamashita, Mitsuo; Sakai, Yoshihiro

2018-03-01

Stress corrosion cracking (SCC) behavior of the hardening-treated materials of 13Cr stainless steel was examined with SSRT tests and constant load tests. In the simulated geothermal water and even in the test water without addition of impurities, the hardening-treated materials showed a brittle intergranular fracture due to the sensitization, which was caused by the present hardening-treatments.

The combined effects of prior-corrosion and aggressive chemical environments on fatigue crack growth behavior in aluminum alloy 7075-T651

NASA Astrophysics Data System (ADS)

Mills, Thomas Brian

1997-11-01

Exfoliation corrosion is a potentially severe form of corrosion that frequently affects high-strength aluminum, particularly 2xxx- and 7xxx-series alloys. Exfoliation degrades components such as sheets, plates, and extrusions that have highly elongated grain structures. Few attempts have been made to investigate the effects of this form of corrosion on the fatigue performance of these materials, so a preliminary study was conducted to determine the effects of exfoliation corrosion on the fatigue response of quarter-inch 7075-T651 aluminum alloy plate. This was accomplished by subjecting aluminum panels to an ASTM standard corrosive solution known as EXCO then fatiguing the panels in corrosion fatigue environments of dry air, humid air, and artificial acid rain. Statistical analyses of the fatigue crack growth data suggest that prior-corrosion and corrosion fatigue are competing mechanisms that both have the potential of accelerating crack growth rates. In the dry air cases, exfoliation accelerated crack growth rates a maximum of 4.75 times over the uncorroded material at lower stress intensities such as 5 ksi surdinch. This accelerated behavior dropped off rapidly, however, and was nonexistent at higher stress intensities. Humid air increased crack velocities considerably as compared to the dry air uncorroded case, but the addition of exfoliation corrosion to the humid cases did not have a significant effect on crack growth behavior. On the other hand, specimens containing exfoliation corrosion and then exposed to artificial acid rain had significantly higher crack growth rates than their uncorroded counterparts. Finally, fractographic examinations of the specimens revealed evidence of lower energy, quasi-cleavage fracture persisting near to the exfoliated edge of specimens tested in the dry air, humid air, and artificial acid rain environments. The implications of this research are that prior-corrosion damage has the ability to significantly increase crack growth rates in this material, and this could render unconservative the inspection intervals determined by damage tolerant analyses based on pristine, uncorroded structure in aircraft where this alloy and damage mechanism are present. The problem is further compounded in the event that prior-corrosion damage and corrosion fatigue act synergisticaliy to increase cracking rates.

Development of Fatigue and Crack Propagation Design and Analysis Methodology in a Corrosive Environment for Typical Mechanically-Fastened Joints. Volume 2. State-of-the-Art Assessment.

DTIC Science & Technology

1983-03-01

120] hypothesized a linear summation model to predict the corrosion -fatigue behavior above Kjscc for a high-strength steel . The model considers the...120] could satisfactorily predict the rates of corrosion -fatigue-crack growth for 18-Ni Maraging steels tested in several gaseous and aqueous...NADC-83126-60 Vol. II 6. The corrosion fatigue behavior of titanium alloys is very complex. Therefore, a better understanding of corrosion fatigue

Characterizing the effect of creep on stress corrosion cracking of cold worked Alloy 690 in supercritical water environment

NASA Astrophysics Data System (ADS)

Zhang, Lefu; Chen, Kai; Du, Donghai; Gao, Wenhua; Andresen, Peter L.; Guo, Xianglong

2017-08-01

The effect of creep on stress corrosion cracking (SCC) was studied by measuring crack growth rates (CGRs) of 30% cold worked (CW) Alloy 690 in supercritical water (SCW) and inert gas environments at temperatures ranging from 450 °C to 550 °C. The SCC crack growth rate under SCW environments can be regarded as the cracking induced by the combined effect of corrosion and creep, while the CGR in inert gas environment can be taken as the portion of creep induced cracking. Results showed that the CW Alloy 690 sustained high susceptibility to intergranular (IG) cracking, and creep played a dominant role in the SCC crack growth behavior, contributing more than 80% of the total crack growth rate at each testing temperature. The temperature dependence of creep induced CGRs follows an Arrhenius dependency, with an apparent activation energy (QE) of about 225 kJ/mol.

Effect of chemical etching and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide resulting from manufacturing process.

PubMed

Shabalovskaya, S; Rondelli, G; Anderegg, J; Simpson, B; Budko, S

2003-07-15

The effect of chemical etching in a HF/HNO(3) acid solution and aging in boiling water on the corrosion resistance of Nitinol wires with black oxide has been evaluated with the use of potentiodynamic, modified potentiostatic ASTM F746, and scratch tests. Scanning-electron microscopy, elemental XPS, and Auger analysis were employed to characterize surface alterations induced by surface treatment and corrosion testing. The effect of aging in boiling water on the temperatures of martensitic transformations and shape recovery was evaluated by means of measuring the wire electroresistance. After corrosion tests, as-received wires revealed uniformly cracked surfaces reminiscent of the stress-corrosion-cracking phenomenon. These wires exhibited negative breakdown potentials in potentiostatic tests and variable breakdown potentials in potentiodynamic tests (- 100 mV to + 400 mV versus SCE). Wires with treated surfaces did not reveal cracking or other traces of corrosion attacks in potentiodynamic tests up to + 900-1400-mV potentials and no pitting after stimulation at + 800 mV in potentiostatic tests. They exhibited corrosion behavior satisfactory for medical applications. Significant improvement of corrosion parameters was observed on the reverse scans in potentiodynamic tests after exposure of treated wires to potentials > 1000 mV. In scratch tests, the prepared surfaces repassivated only at low potentials, comparable to that of stainless steel. Tremendous improvement of the corrosion behavior of treated Nitinol wires is associated with the removal of defect surface material and the growth of stable TiO(2) oxide. The role of precipitates in the corrosion resistance of Nitinol-scratch repassivation capacity in particular-is emphasized in the discussion. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 331-340, 2003

Stress Corrosion Cracking of Certain Aluminum Alloys

NASA Technical Reports Server (NTRS)

Hasse, K. R.; Dorward, R. C.

1983-01-01

SC resistance of new high-strength alloys tested. Research report describes progress in continuing investigation of stress corrosion (SC) cracking of some aluminum alloys. Objective of program is comparing SC behavior of newer high-strength alloys with established SC-resistant alloy.

The Delayed Fracture of Aluminum Alloys.

DTIC Science & Technology

1981-01-01

Cracking of a Maraging Steel ," Corrosion NACE, 1971, vol. 27, no. 10, pp. 429-433. 42. H.R. Smith and D.E. Piper: "Stress- Corrosion Testing with Pre...Sivaramakrishman, and R. Kumar: "Influence of Processing Variables on the Stress Corrosion Characteristics of Weldable Al-Zn-Mg Alloys," Light Met. Age , 1979...if necessary and Identify by block number) aluminum alloys, stress- corrosion cracking, oxide film, Auger electron spectroscopy, Auger depth profiling

Corrosion characteristics of nickel alloys. Citations from the International Aerospace Abstracts data base

NASA Technical Reports Server (NTRS)

Zollars, G. F.

1979-01-01

This bibliography cites 118 articles from the international literature concerning corrosion characteristics of nickel alloys. Articles dealing with corrosion resistance, corrosion tests, intergranular corrosion, oxidation resistance, and stress corrosion cracking of nickel alloys are included.

Review on stress corrosion and corrosion fatigue failure of centrifugal compressor impeller

NASA Astrophysics Data System (ADS)

Sun, Jiao; Chen, Songying; Qu, Yanpeng; Li, Jianfeng

2015-03-01

Corrosion failure, especially stress corrosion cracking and corrosion fatigue, is the main cause of centrifugal compressor impeller failure. And it is concealed and destructive. This paper summarizes the main theories of stress corrosion cracking and corrosion fatigue and its latest developments, and it also points out that existing stress corrosion cracking theories can be reduced to the anodic dissolution (AD), the hydrogen-induced cracking (HIC), and the combined AD and HIC mechanisms. The corrosion behavior and the mechanism of corrosion fatigue in the crack propagation stage are similar to stress corrosion cracking. The effects of stress ratio, loading frequency, and corrosive medium on the corrosion fatigue crack propagation rate are analyzed and summarized. The corrosion behavior and the mechanism of stress corrosion cracking and corrosion fatigue in corrosive environments, which contain sulfide, chlorides, and carbonate, are analyzed. The working environments of the centrifugal compressor impeller show the behavior and the mechanism of stress corrosion cracking and corrosion fatigue in different corrosive environments. The current research methods for centrifugal compressor impeller corrosion failure are analyzed. Physical analysis, numerical simulation, and the fluid-structure interaction method play an increasingly important role in the research on impeller deformation and stress distribution caused by the joint action of aerodynamic load and centrifugal load.

SRNL SHELF LIFE STUDIES - SCC STUDIES AT ROOM TEMPERTURE [stress corrosion cracking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mickalonis, J.; Duffey, J.

Phase II, Series 2 corrosion testing performed by the Savannah River National Laboratory (SRNL) for the Department of Energy 3013 container has been completed. The corrosion tests are part of an integrated plan conducted jointly by Los Alamos National Laboratory and the Savannah River Site. SRNL was responsible for conducting corrosion studies in small-scale vessels to address the influence of salt composition, water loading, and type of oxide/salt contact on the relative humidity inside a 3013 container and on the resulting corrosion of Type 304L and 316L stainless steel (304L and 316L). This testing was conducted in two phases: Phasemore » I evaluated a broad spectrum of salt compositions and initial water loadings on the salt mixtures exposed to 304L and 316L and the resulting corrosion; Phase II evaluated the corrosion of 304L at specific water loadings and a single salt composition. During Phase I testing at high initial moisture levels (0.35 to 1.24 wt%)a, the roomtemperature corrosion of 304L exposed to a series of plutonium oxide/chloride salt mixtures ranged from superficial staining to pitting and stress corrosion cracking (SCC). 304L teardrop coupons that exhibited SCC were directly exposed to a mixture composed of 98 wt % PuO2, 0.9 wt % NaCl, 0.9 wt % KCl, and 0.2 wt % CaCl2. Cracking was not observed in a 316L teardrop coupon. Pitting was also observed in this environment for both 304L and 316L with depths ranging from 20 to 100 μm. Neither pitting nor SCC was observed in mixtures with a greater chloride salt concentration (5 and 28 wt%). These results demonstrated that for a corrosive solution to form a balance existed between the water loading and the salt chloride concentration. This chloride solution results from the interaction of loaded water with the hydrating CaCl2 salt. In Phase II, Series 1 tests, the SCC results were shown to be reproducible with cracking occurring in as little as 85 days. The approximate 0.5 wt% moisture level was found to result in an initial relative humidity of ~55% within the small-scale vessels. Pits were found to be associated with cracks and appeared to act as initiators for the cracking. In a vapor-space only exposure, the weld oxide, which results from the TIG closure weld used to fabricate the teardrop coupon, was also shown to be more susceptible to pitting corrosion than a surface free from weld oxide. This result has important implications for the closure weld of the 3013 inner can since the weld oxide on the can internal surface cannot be removed. The results from the Phase II, Series 2 tests further demonstrated the significance of forming a solution with a critical chloride concentration for corrosion to proceed. 304L teardrop coupons were found to corrode only by pitting with a similar oxide/salt mixture as used in Series 1 testing but with a lower water loading of 0.2 wt%, which resulted in an initial relative humidity of 35-38%. These tests ran twice as long as those for Series 1 testing. The exposure condition was also found to impact the corrosion with salt-exposed surfaces showing lower corrosion resistance. Additional analyses of the Series 2 coupons are recommended especially for determining if cracks emanate from the bottom of pits. Data generated under the 2009 3013 corrosion test plan, as was presented here, increased the understanding of the corrosion process within a sealed 3013 container. Along with the corrosion data from destructive evaluations of 3013 containers, the inner can closure weld region (ICCWR) has been identified as the most vulnerable area of the inner can where corrosion may lead to corrosive species leaking to the interior surface of the outer container, thereby jeopardizing the integrity of the 3013 container. A new corrosion plan has been designed that will characterize the corrosion at the ICCWR of 3013 DEs as well as parameters affecting this corrosion.« less

Stress corrosion cracking of an aluminum alloy used in external fixation devices.

PubMed

Cartner, Jacob L; Haggard, Warren O; Ong, Joo L; Bumgardner, Joel D

2008-08-01

Treatment for compound and/or comminuted fractures is frequently accomplished via external fixation. To achieve stability, the compositions of external fixators generally include aluminum alloy components due to their high strength-to-weight ratios. These alloys are particularly susceptible to corrosion in chloride environments. There have been several clinical cases of fixator failure in which corrosion was cited as a potential mechanism. The aim of this study was to evaluate the effects of physiological environments on the corrosion susceptibility of aluminum 7075-T6, since it is used in orthopedic external fixation devices. Electrochemical corrosion curves and alternate immersion stress corrosion cracking tests indicated aluminum 7075-T6 is susceptible to corrosive attack when placed in physiological environments. Pit initiated stress corrosion cracking was the primary form of alloy corrosion, and subsequent fracture, in this study. Anodization of the alloy provided a protective layer, but also caused a decrease in passivity ranges. These data suggest that once the anodization layer is disrupted, accelerated corrosion processes occur. (c) 2007 Wiley Periodicals, Inc.

Corrosion and Corrosion-Fatigue Behavior of 7075 Aluminum Alloys Studied by In Situ X-Ray Tomography

NASA Astrophysics Data System (ADS)

Stannard, Tyler

7XXX Aluminum alloys have high strength to weight ratio and low cost. They are used in many critical structural applications including automotive and aerospace components. These applications frequently subject the alloys to static and cyclic loading in service. Additionally, the alloys are often subjected to aggressive corrosive environments such as saltwater spray. These chemical and mechanical exposures have been known to cause premature failure in critical applications. Hence, the microstructural behavior of the alloys under combined chemical attack and mechanical loading must be characterized further. Most studies to date have analyzed the microstructure of the 7XXX alloys using two dimensional (2D) techniques. While 2D studies yield valuable insights about the properties of the alloys, they do not provide sufficiently accurate results because the microstructure is three dimensional and hence its response to external stimuli is also three dimensional (3D). Relevant features of the alloys include the grains, subgrains, intermetallic inclusion particles, and intermetallic precipitate particles. The effects of microstructural features on corrosion pitting and corrosion fatigue of aluminum alloys has primarily been studied using 2D techniques such as scanning electron microscopy (SEM) surface analysis along with post-mortem SEM fracture surface analysis to estimate the corrosion pit size and fatigue crack initiation site. These studies often limited the corrosion-fatigue testing to samples in air or specialized solutions, because samples tested in NaCl solution typically have fracture surfaces covered in corrosion product. Recent technological advancements allow observation of the microstructure, corrosion and crack behavior of aluminum alloys in solution in three dimensions over time (4D). In situ synchrotron X-Ray microtomography was used to analyze the corrosion and cracking behavior of the alloy in four dimensions to elucidate crack initiation at corrosion pits for samples of multiple aging conditions and impurity concentrations. Additionally, chemical reactions between the 3.5 wt% NaCl solution and the crack surfaces were quantified by observing the evolution of hydrogen bubbles from the crack. The effects of the impurity particles and age-hardening particles on the corrosion and fatigue properties were examined in 4D.

Study of the Effect of Swelling on Irradiation Assisted Stress Corrosion Cracking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teysseyre, Sebastien Paul

2016-09-01

This report describes the methodology used to study the effect of swelling on the crack growth rate of an irradiation-assisted stress corrosion crack that is propagating in highly irradiated stainless steel 304 material irradiated to 33 dpa in the Experimental Breeder Reactor-II. The material selection, specimens design, experimental apparatus and processes are described. The results of the current test are presented.

Effect of Thermomechanical Processing and Crystallographic Orientation on the Corrosion Behavior of API 5L X70 Pipeline Steel

NASA Astrophysics Data System (ADS)

Ohaeri, Enyinnaya; Omale, Joseph; Eduok, Ubong; Szpunar, Jerzy

2018-04-01

This work presents the electrochemical response of X70 pipeline steel substrates thermomechanically processed at different conditions. The WE sample was hot rolled at a temperature range of 850 °C to 805 °C and cooled at a rate of 42.75 °C/s. Another sample WD was hot rolled from 880 °C to 815 °C and cooled at a faster rate of 51.5 °C/s. Corrosion tests were conducted electrochemically by potentiodynamic polarization in hydrogen-charged and non-hydrogen-charged environments. A lower corrosion rate was measured with hydrogen charging due to the rapid formation of corrosion product film on pipeline substrate, but WE specimen emerged as the most susceptible to corrosion with and without hydrogen charging. Variations in thermomechanical rolling conditions influenced grain orientation, protective film properties, corrosion, and cracking behavior on both specimens. Cracks were seen in both specimens after hydrogen charging, but specimen WE experienced a more intense deterioration of protective corrosion product film and subsequent cracking. A large part of specimen WD retained its protective corrosion product film after the polarization test, and sites where spalling occurred resulted in pitting with less cracking. Despite weak crystallographic texture noticed in both specimens, WD showed a higher intensity of corrosion-resistant 111||ND-oriented grains, while WE showed a more random distribution of 111||ND-, 011||ND-, and 001||ND-oriented grains with a lower intensity.

Effect of Thermomechanical Processing and Crystallographic Orientation on the Corrosion Behavior of API 5L X70 Pipeline Steel

NASA Astrophysics Data System (ADS)

Ohaeri, Enyinnaya; Omale, Joseph; Eduok, Ubong; Szpunar, Jerzy

2018-06-01

This work presents the electrochemical response of X70 pipeline steel substrates thermomechanically processed at different conditions. The WE sample was hot rolled at a temperature range of 850 °C to 805 °C and cooled at a rate of 42.75 °C/s. Another sample WD was hot rolled from 880 °C to 815 °C and cooled at a faster rate of 51.5 °C/s. Corrosion tests were conducted electrochemically by potentiodynamic polarization in hydrogen-charged and non-hydrogen-charged environments. A lower corrosion rate was measured with hydrogen charging due to the rapid formation of corrosion product film on pipeline substrate, but WE specimen emerged as the most susceptible to corrosion with and without hydrogen charging. Variations in thermomechanical rolling conditions influenced grain orientation, protective film properties, corrosion, and cracking behavior on both specimens. Cracks were seen in both specimens after hydrogen charging, but specimen WE experienced a more intense deterioration of protective corrosion product film and subsequent cracking. A large part of specimen WD retained its protective corrosion product film after the polarization test, and sites where spalling occurred resulted in pitting with less cracking. Despite weak crystallographic texture noticed in both specimens, WD showed a higher intensity of corrosion-resistant 111|| ND-oriented grains, while WE showed a more random distribution of 111|| ND-, 011|| ND-, and 001|| ND-oriented grains with a lower intensity.

Aqueous chloride stress corrosion cracking of titanium - A comparison with environmental hydrogen embrittlement

NASA Technical Reports Server (NTRS)

Nelson, H. G.

1974-01-01

The physical characteristics of stress corrosion cracking of titanium in an aqueous chloride environment are compared with those of embrittlement of titanium by a gaseous hydrogen environment in an effort to help contribute to the understanding of the possible role of hydrogen in the complex stress corrosion cracking process. Based on previous studies, the two forms of embrittlement are shown to be similar at low hydrogen pressures (100 N/sq m) but dissimilar at higher hydrogen pressures. In an effort to quantify this comparison, tests were conducted in an aqueous chloride solution using the same material and test techniques as had previously been employed in a gaseous hydrogen environment. The results of these tests strongly support models based on hydrogen as the embrittling species in an aqueous chloride environment.

Prediction of stress corrosion of carbon steel by nuclear process liquid wastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ondrejcin, R.S.

1978-08-01

Radioactive liquid wastes are produced as a consequence of processing fuel from Savannah River Plant (SRP) production reactors. These wastes are stored in mild steel waste tanks, some of which have developed cracks from stress corrosion. A laboratory test was developed to determine the relative agressiveness of the wastes for stress corrosion cracking of mild steel. Tensile samples were strained to fracture in synthetic waste solutions in an electrochemical cell with the sample as the anode. Crack initiation is expected if total elongation of the steel in the test is less than its uniform elongation in air. Cracking would bemore » anticipated in a plant waste tank if solution conditions were equivalent to test conditions that cause a total elongation that is less than uniform elongation. The electrochemical tensile tests showed that the supernates in salt receiver tanks at SRP have the least aggressive compositions, and wastes newly generated during fuel repocessing have the most aggressive ones. Test data also verified that ASTM A 516-70 steel used in the fabrication of the later design waste tanks is less susceptible to cracking than the ASTM A 285-B steel used in earlier designs.« less

Study on Corrosion-induced Crack Initiation and Propagation of Sustaining Loaded RCbeams

NASA Astrophysics Data System (ADS)

Zhong, X. P.; Li, Y.; Yuan, C. B.; Yang, Z.; Chen, Y.

2018-05-01

For 13 pieces of reinforced concrete beams with HRB500 steel bars under long-term sustained loads, at time of corrosion-induced initial crack of concrete, and corrosion-induced crack widths of 0.3mm and 1mm, corrosion of steel bars and time-varying behavior of corrosion-induced crack width were studied by the ECWD (Electro-osmosis - constant Current – Wet and Dry cycles) accelerated corrosion method. The results show that when cover thickness was between 30 and 50mm,corrosion rates of steel bars were between 0.8% and 1.7% at time of corrosion-induced crack, and decreased with increasing concrete cover thickness; when corrosion-induced crack width was 0.3mm, the corrosion rate decreased with increasing steel bar diameter, and increased with increasing cover thickness; its corrosion rate varied between 0.98% and 4.54%; when corrosion-induced crack width reached 1mm, corrosion rate of steel bars was between 4% and 4.5%; when corrosion rate of steel bars was within 5%, the maximum and average corrosion-induced crack and corrosion rate of steel bars had a good linear relationship. The calculation model predicting the maximum and average width of corrosion-induced crack is given in this paper.

49 CFR 180.352 - Requirements for retest and inspection of IBCs.

Code of Federal Regulations, 2010 CFR

2010-10-01

... qualification tests. The IBC must be externally inspected for cracks, warpage, corrosion or any other damage... IBC must be internally inspected for cracks, warpage, and corrosion or any other defect that might.... Inner protrusions which could puncture or abrade the liner must be covered. (d) Requirements applicable...

Structural Area Inspection Frequency Evaluation (SAIFE). Volume III. Demonstration Input, Inspection Survey, and MRR Data

DTIC Science & Technology

1978-04-01

3 1.7 Production Rate Change Time . . . . 3 1.8 Time of Fatigue Test Start . ..... 3 1.9 Fatigue Test Acceleration Factor . 3 1.10 Corrosion...simulation logic. SAIFE accounts for the following factors : (1) aircraft design analysis; (2) component and full-scale fatigue testing; (3) production ...reliability; production , servi ce,Information Service, Springfield, and corrosion defects; crack or corrosi on Virginia 22151 detection probability; crack

Water corrosion of F82H-modified in simulated irradiation conditions by heat treatment

NASA Astrophysics Data System (ADS)

Lapeña, J.; Blázquez, F.

2000-12-01

This paper presents results of testing carried out on F82H in water at 260°C with 2 ppm H 2 and the addition of 0.27 ppm Li in the form of LiOH. Uniform corrosion tests have been carried out on as-received material and on specimens from welded material [TIG and electron beam (EB)]. Stress corrosion cracking (SCC) tests have been carried out in as-received material and in material heat treated to simulate neutron irradiation hardening (1075°C/30' a.c. and 1040°C/30' + 625°C/1 h a.c.) with hardness values of 405 and 270 HV30, respectively. Results for uniform corrosion after 2573 h of testing have shown weight losses of about 60 mg/dm 2. Compact tension (CT) specimens from the as-received material tested under constant load have not experienced crack growth. However, in the simulated irradiation conditions for a stress intensity factor between 40 and 80 MPa√m, crack growth rates of about 7×10 -8 m/s have been measured.

Quantitative sensing of corroded steel rebar embedded in cement mortar specimens using ultrasonic testing

NASA Astrophysics Data System (ADS)

Owusu Twumasi, Jones; Le, Viet; Tang, Qixiang; Yu, Tzuyang

2016-04-01

Corrosion of steel reinforcing bars (rebars) is the primary cause for the deterioration of reinforced concrete structures. Traditional corrosion monitoring methods such as half-cell potential and linear polarization resistance can only detect the presence of corrosion but cannot quantify it. This study presents an experimental investigation of quantifying degree of corrosion of steel rebar inside cement mortar specimens using ultrasonic testing (UT). A UT device with two 54 kHz transducers was used to measure ultrasonic pulse velocity (UPV) of cement mortar, uncorroded and corroded reinforced cement mortar specimens, utilizing the direct transmission method. The results obtained from the study show that UPV decreases linearly with increase in degree of corrosion and corrosion-induced cracks (surface cracks). With respect to quantifying the degree of corrosion, a model was developed by simultaneously fitting UPV and surface crack width measurements to a two-parameter linear model. The proposed model can be used for predicting the degree of corrosion of steel rebar embedded in cement mortar under similar conditions used in this study up to 3.03%. Furthermore, the modeling approach can be applied to corroded reinforced concrete specimens with additional modification. The findings from this study show that UT has the potential of quantifying the degree of corrosion inside reinforced cement mortar specimens.

Corrosion fatigue studies on a bulk glassy Zr-based alloy under three-point bending

NASA Astrophysics Data System (ADS)

Grell, Daniel; Wilkin, Yannic; Gostin, Petre F.; Gebert, Annett; Kerscher, Eberhard

2016-12-01

Corrosion fatigue (CF) tests were carried out on bulk glassy Zr52.5Cu17.9Al10Ni14.6Ti5 (Vitreloy 105) samples under load-controlled three-point bending conditions with a load ratio of R = 0.1 in 0.01 M Na2SO4 + 0.01 M NaCl electrolyte. During cyclic testing, the bar-shaped specimens were polarized in situ at constant potentials and the current was monitored. Three different anodic potentials within the interval between the pitting potential EP and the repassivation potential ER, and three different load amplitudes were applied. In some cases, in situ microscopic observations revealed the formation of black corrosion products in the vicinity of the crack tip during anodic polarization. Fractographic analysis revealed a clear distinction between two modes of crack growth characterized by smooth dissolution induced regions on the one hand and slim fast fracture areas on the other hand. Both alternating features contributed to a broad striated corrosion fatigue fracture surface. Moreover, further fatigue tests were carried out under free corrosion conditions yielding additional information on crack initiation and crack propagation period by means of the open circuit potential (OCP) changes. Thereby, a slight increase in OCP was detected after rupture of the passive layer due to bare metal exposed to the electrolyte. The electrochemical response increased continuously according to stable crack propagation until fracture occurred. Finally, the fracture surfaces of the corrosion fatigue samples were investigated by energy dispersive X-ray with the objective of analyzing the elemental distribution after anodic dissolution. Interestingly, anodic polarization at a near repassivation potential of -50 mV vs. SCE (Saturated Calomel Electrode, E = 0.241 V vs. SHE, Standard Hydrogen Electrode) led to favorable effects on the fatigue lifetime. In conclusion, all results are conflated to a corrosion fatigue model for bulk glassy Vitreloy 105 under anodic polarization in chloride-containing electrolyte and compared to the previously proposed stress corrosion mechanisms under similar conditions.

Stress corrosion cracking and corrosion fatigue characterisation of MgZn1Ca0.3 (ZX10) in a simulated physiological environment.

PubMed

Jafari, Sajjad; Raman, R K Singh; Davies, Chris H J; Hofstetter, Joelle; Uggowitzer, Peter J; Löffler, Jörg F

2017-01-01

Magnesium (Mg) alloys have attracted great attention as potential materials for biodegradable implants. It is essential that an implant material possesses adequate resistance to cracking/fracture under the simultaneous actions of corrosion and mechanical stresses, i.e., stress corrosion cracking (SCC) and/or corrosion fatigue (CF). This study investigates the deformation behaviour of a newly developed high-strength low-alloy Mg alloy, MgZn1Ca0.3 (ZX10), processed at two different extrusion temperatures of 325 and 400°C (named E325 and E400, respectively), under slow strain tensile and cyclic tension-compression loadings in air and modified simulated body fluid (m-SBF). Extrusion resulted in a bimodal grain size distribution with recrystallised grain sizes of 1.2 μm ± 0.8 μm and 7 ± 5 μm for E325 and E400, respectively. E325 possessed superior tensile and fatigue properties to E400 when tested in air. This is mainly attributed to a grain-boundary strengthening mechanism. However, both E325 and E400 were found to be susceptible to SCC at a strain rate of 3.1×10 -7 s -1 in m-SBF. Moreover, both E325 and E400 showed similar fatigue strength when tested in m-SBF. This is explained on the basis of crack initiation from localised corrosion following tests in m-SBF. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Real time monitoring of environmental crack growth in BWRs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hale, D.; Diehl, C.G.

1988-01-01

A comprehensive field test program was recently completed at several Boiling Water Reactors (BWR) to quantify the effect of coolant impurities on the initiation and growth of stress corrosion cracks. A new technology was utilized which allows for real time monitoring of stress corrosion crack growth rates. The BWR environments were characterized using Ion Chromatography and Electro Chemical Potential (ECP) measurements. The effects of typical water chemistry transients and startups were quantified.

An improved stress corrosion test medium for aluminum alloys

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Coston, J. E.

1981-01-01

A laboratory test method that is only mildly corrosive to aluminum and discriminating for use in classifying the stress corrosion cracking resistance of aluminum alloys is presented along with the method used in evaluating the media selected for testing. The proposed medium is easier to prepare and less expensive than substitute ocean water.

Apollo experience report: The problem of stress-corrosion cracking

NASA Technical Reports Server (NTRS)

Johnson, R. E.

1973-01-01

Stress-corrosion cracking has been the most common cause of structural-material failures in the Apollo Program. The frequency of stress-corrosion cracking has been high and the magnitude of the problem, in terms of hardware lost and time and money expended, has been significant. In this report, the significant Apollo Program experiences with stress-corrosion cracking are discussed. The causes of stress-corrosion cracking and the corrective actions are discussed, in terminology familiar to design engineers and management personnel, to show how stress-corrosion cracking can be prevented.

Cyclic stress effect on stress corrosion cracking of duplex stainless steel in chloride and caustic solutions

NASA Astrophysics Data System (ADS)

Yang, Di

Duplex stainless steel (DSS) is a dual-phase material with approximately equal volume amount of austenite and ferrite. It has both great mechanical properties (good ductility and high tensile/fatigue strength) and excellent corrosion resistance due to the mixture of the two phases. Cyclic loadings with high stress level and low frequency are experienced by many structures. However, the existing study on corrosion fatigue (CF) study of various metallic materials has mainly concentrated on relatively high frequency range. No systematic study has been done to understand the ultra-low frequency (˜10-5 Hz) cyclic loading effect on stress corrosion cracking (SCC) of DSSs. In this study, the ultra-low frequency cyclic loading effect on SCC of DSS 2205 was studied in acidified sodium chloride and caustic white liquor (WL) solutions. The research work focused on the environmental effect on SCC of DSS 2205, the cyclic stress effect on strain accumulation behavior of DSS 2205, and the combined environmental and cyclic stress effect on the stress corrosion crack initiation of DSS 2205 in the above environments. Potentiodynamic polarization tests were performed to investigate the electrochemical behavior of DSS 2205 in acidic NaCl solution. Series of slow strain rate tests (SSRTs) at different applied potential values were conducted to reveal the optimum applied potential value for SCC to happen. Room temperature static and cyclic creep tests were performed in air to illustrate the strain accumulation effect of cyclic stresses. Test results showed that cyclic loading could enhance strain accumulation in DSS 2205 compared to static loading. Moreover, the strain accumulation behavior of DSS 2205 was found to be controlled by the two phases of DSS 2205 with different crystal structures. The B.C.C. ferrite phase enhanced strain accumulation due to extensive cross-slips of the dislocations, whereas the F.C.C. austenite phase resisted strain accumulation due to cyclic strain hardening. Cyclic SSRTs were performed under the conditions that SCC occurs in sodium chloride and WL solutions. Test results show that cyclic stress facilitated crack initiations in DSS 2205. Stress corrosion cracks initiated from the intermetallic precipitates in acidic chloride environment, and the cracks initiated from austenite phase in WL environment. Cold-working has been found to retard the crack initiations induced by cyclic stresses.

Behavior of Fatigue Crack Tip Opening in Air and Corrosive Atmosphere

NASA Astrophysics Data System (ADS)

Hayashi, Morihito; Toeda, Kazunori

In the study, a formula for predicting fatigue crack tip opening displacement is deduced firstly. And then, due to comparing actual crack growth rate with the deduced formula, the crack tip configuration factor is defined to figure out the crack tip opening configuration that is useful to clarify the behavior of fatigue crack tip formation apparently. Applying the concept, the crack growth of 7/3 brass and 6/4 brass is predicted from the formula, by replacing material properties such as plastic flow resistance, Young modulus, the Poisson ratio, and fatigue toughness, and fatigue test conditions such as the stress intensity factor range, the load ratio, and cycle frequency. Furthermore, the theoretically expected results are verified with the fatigue tests which were carried out on CT specimens under different load conditions of load ratio, cycle frequency, and cyclic peak load, in different environments of air or corrosive ammonia atmosphere, for various brasses. And by comparing and discussing the calculated crack growth rate with attained experimental results, the apparent configuration factor at the crack tip is determined. And through the attained factor which changes along with crack growth, the behaviors of fatigue crack tip formation under different test conditions have been found out.

Fatigue in the Presence of Corrosion (Fatigue sous corrosion)

DTIC Science & Technology

1999-03-01

Fatigue Crack Growth Propagation of Aluminum Lithium cycle managers to safely delay repairs to a more appropriate Alloys " described the effect of... effects of service corrosion on fatigue lab tests with 2024 -T3, because 7178 life , if any, can be established in this was not available. However, we did not... life and the fatigue crack growth behavior of the cases where a structural member is the 2024 alloy was studied as well. stressed or fatigued

Comparative Studies on microstructure, mechanical and corrosion behaviour of DMR 249A Steel and its welds

NASA Astrophysics Data System (ADS)

Mohammed, Raffi; Dilkush; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

DMR249A Medium strength (low carbon) Low-alloy steels are used as structural components in naval applications due to its low cost and high availability. An attempt has been made to weld the DMR 249A steel plates of 8mm thickness using shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW). Welds were characterized for metallography to carry out the microstructural changes, mechanical properties were evaluated using vickers hardness tester and universal testing machine. Potentio-dynamic polarization tests were carried out to determine the pitting corrosion behaviour. Constant load type Stress corrosion cracking (SCC) testing was done to observe the cracking tendency of the joints in a 3.5%NaCl solution. Results of the present study established that SMA welds resulted in formation of relatively higher amount of martensite in ferrite matrix when compared to gas tungsten arc welding (GTAW). It is attributed to faster cooling rates achieved due to high thermal efficiency. Improved mechanical properties were observed for the SMA welds and are due to higher amount of martensite. Pitting corrosion and stress corrosion cracking resistance of SMA welds were poor when compared to GTA welds.

A Contribution to Proof the Component Integrity Taking Into Account the Corrosion-Assisted Crack Growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roos, Eberhard; Otremba, Frank; Huttner, Frank

2002-07-01

The proof of the component integrity is fundamental for a safe and reliable operation of Nuclear Power Plants (NPP). The concept of the Material Testing Institute (MPA) for integrity assessment is based on fracture mechanic analysis which results in detailed regulations for nondestructive examination. This approach has to account for the main damage mechanisms as fatigue and corrosion. This paper focuses on the influence of corrosion-assisted crack growth which strongly depends on corrosion and environmental conditions (e.g. coolant purity). Up to stress intensity of approximately 60 MPam for ferritic low-alloy steels in high-purity water (acc. to specification) under constant loadmore » conditions the analysis can be based on a crack extension of max. 70 for each load cycle. Related to a test duration of 1000 hours this is equivalent to a formally calculated crack growth rate (CGR) of = 2 10{sup -8} mm/s. For austenitic stainless steels more complex dependences on material, environmental and mechanical parameters exist. Particularly, for stabilized austenitic steels the crack growth rate data base is relatively weak. Under unfavourable environmental conditions in single cases crack growth rates up to 6 mm/a have been measured. Based on experimental results an arithmetic mean value of 0.95 mm/a and a median value of 0.6 mm/a have been determined. A further improvement of data base is desirable. (authors)« less

Stress Corrosion-Cracking and Corrosion Fatigue Impact of IZ-C17+ Zinc Nickel on 4340 Steel

DTIC Science & Technology

2017-05-17

REPORT NO: NAWCADPAX/TIM-2016/189 STRESS CORROSION-CRACKING AND CORROSION FATIGUE IMPACT OF IZ-C17+ ZINC-NICKEL ON 4340 STEEL by...CORROSION-CRACKING AND CORROSION FATIGUE IMPACT OF IZ-C17+ ZINC-NICKEL ON 4340 STEEL by Craig Matzdorf Charles Lei Matt Stanley...5a. CONTRACT NUMBER STRESS CORROSION-CRACKING AND CORROSION FATIGUE IMPACT OF IZ-C17+ ZINC-NICKEL ON 4340 STEEL 5b. GRANT NUMBER 5c. PROGRAM

CRACK GROWTH RESPONSE OF ALLOY 690 IN SIMULATED PWR PRIMARY WATER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toloczko, Mychailo B.; Bruemmer, Stephen M.

2009-12-01

The stress corrosion crack growth response of three extruded alloy 690 CRDM tube heats was investigated in several thermomechanical conditions. Extremely low propagation rates (< 1 x 10{sup -9} mm/s) were observed under constant stress intensity factor (K) loading at 325-350 C in the as-received, thermally treated (TT) materials despite using a variety of transitioning techniques. Post-test observation of the crack-growth surfaces revealed only isolated intergranular (IG) cracking. One-dimensional cold rolling to 17% reduction and testing in the S-L orientation did not promote enhanced stress corrosion rates. However, somewhat higher propagation rates were observed in a 30% cold-rolled alloy 690TTmore » specimen tested in the T-L orientation. Cracking of the cold-rolled material was promoted on grain boundaries oriented parallel to the rolling plane with the % IG increasing with the amount of cold rolling.« less

Effect of Microstructure on Stress Corrosion Cracking Behaviour of High Nitrogen Stainless Steel Gas Tungsten Arc Welds

NASA Astrophysics Data System (ADS)

Mohammed, Raffi; Srinivasa Rao, K.; Madhusudhan Reddy, G.

2018-03-01

Present work is aimed to improve stress corrosion cracking resistance of high nitrogen steel and its welds. An attempt to weld high nitrogen steel of 5 mm thick plate using gas tungsten arc welding (GTAW) with three high strength age hardenable fillers i.e., 11-10 PH filler, PH 13- 8Mo and maraging grade of MDN 250 filler is made. Welds were characterized by optical microscopy and scanning electron microscopy. Vickers hardness testing of the welds was carried out to study the mechanical behaviour of welds. Potentio-dynamic polarization studies were done to determine pitting corrosion resistance in aerated 3.5% NaCl solution. Stress corrosion cracking (SCC) testing was carried out using constant load type machine with applied stress of 50% yield strength and in 45% MgCl2 solution boiling at 155°C. The results of the present investigation established that improvement in resistance to stress corrosion cracking was observed for PH 13- 8Mo GTA welds when compared to 11-10 PH and MDN 250 GTA welds. However, All GTA welds failed in the weld interface region. This may be attributed to relatively lower pitting potential in weld interface which acts as active site and the initiation source of pitting.

Test methods for environment-assisted cracking

NASA Astrophysics Data System (ADS)

Turnbull, A.

1992-03-01

The test methods for assessing environment assisted cracking of metals in aqueous solution are described. The advantages and disadvantages are examined and the interrelationship between results from different test methods is discussed. The source of differences in susceptibility to cracking occasionally observed from the varied mechanical test methods arises often from the variation between environmental parameters in the different test conditions and the lack of adequate specification, monitoring, and control of environmental variables. Time is also a significant factor when comparing results from short term tests with long exposure tests. In addition to these factors, the intrinsic difference in the important mechanical variables, such as strain rate, associated with the various mechanical tests methods can change the apparent sensitivity of the material to stress corrosion cracking. The increasing economic pressure for more accelerated testing is in conflict with the characteristic time dependence of corrosion processes. Unreliable results may be inevitable in some cases but improved understanding of mechanisms and the development of mechanistically based models of environment assisted cracking which incorporate the key mechanical, material, and environmental variables can provide the framework for a more realistic interpretation of short term data.

Stress corrosion crack initiation of alloy 600 in PWR primary water

DOE PAGES

Zhai, Ziqing; Toloczko, Mychailo B.; Olszta, Matthew J.; ...

2017-04-27

Stress corrosion crack (SCC) initiation of three mill-annealed alloy 600 heats in simulated pressurized water reactor primary water has been investigated using constant load tests equipped with in-situ direct current potential drop (DCPD) measurement capabilities. SCC initiation times were greatly reduced by a small amount of cold work. Shallow intergranular attack and/or cracks were found on most high-energy grain boundaries intersecting the surface with only a small fraction evolving into larger cracks and intergranular SCC growth. Crack depth profiles were measured and related to DCPD-detected initiation response. Lastly, we discuss processes controlling the SCC initiation in mill-annealed alloy 600.

Stress corrosion crack initiation of alloy 600 in PWR primary water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Ziqing; Toloczko, Mychailo B.; Olszta, Matthew J.

Stress corrosion crack (SCC) initiation of three mill-annealed alloy 600 heats in simulated pressurized water reactor primary water has been investigated using constant load tests equipped with in-situ direct current potential drop (DCPD) measurement capabilities. SCC initiation times were greatly reduced by a small amount of cold work. Shallow intergranular attack and/or cracks were found on most high-energy grain boundaries intersecting the surface with only a small fraction evolving into larger cracks and intergranular SCC growth. Crack depth profiles were measured and related to DCPD-detected initiation response. Lastly, we discuss processes controlling the SCC initiation in mill-annealed alloy 600.

Environmentally assisted cracking in light water reactors. Semiannual report, July 1998-December 1998.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chopra, O. K.; Chung, H. M.; Gruber, E. E.

This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors from July 1998 to December 1998. Topics that have been investigated include (a) environmental effects on fatigue S-N behavior of primary pressure boundary materials, (b) irradiation-assisted stress corrosion cracking of austenitic stainless steels (SSs), and (c) EAC of Alloys 600 and 690. Fatigue tests have been conducted to determine the crack initiation and crack growth characteristics of austenitic SSs in LWR environments. Procedures are presented for incorporating the effects of reactor coolant environments on the fatigue life of pressure vesselmore » and piping steels. Slow-strain-rate tensile tests and posttest fractographic analyses were conducted on several model SS alloys irradiated to {approx}0.3 and 0.9 x 10{sup 21} n {center_dot} cm{sup -2} (E > 1 MeV) in helium at 289 C in the Halden reactor. The results have been used to determine the influence of alloying and impurity elements on the susceptibility of these steels to irradiation-assisted stress corrosion cracking. Fracture toughness J-R curve tests were also conducted on two heats of Type 304 SS that were irradiated to {approx}0.3 x 10{sup 21} n {center_dot} cm{sup -2} in the Halden reactor. Crack-growth-rate tests have been conducted on compact-tension specimens of Alloys 600 and 690 under constant load to evaluate the resistance of these alloys to stress corrosion cracking in LWR environments.« less

Crack Initiation and Growth Behavior at Corrosion Pit in 2024-T3 Aluminum Alloy

DTIC Science & Technology

2014-09-01

63 Figure B.1: The crack length vs. number of cycles during fatigue testing for the 2AI-01 specimen...number of cycles during fatigue testing for the the 2AI- 02 specimen...64 Figure B.3: The crack length vs. number of cycles during fatigue testing for the 2Sl-01 specimen

Flaw growth of 7075, 7475, 7050 and 7049 aluminum alloy plate in stress corrosion environments: 4-year marine atmosphere results

NASA Technical Reports Server (NTRS)

Hasse, K. R.; Dorward, R. C.

1981-01-01

After nearly 53 months of exposure to marine atmosphere, crack growth in SL DCB specimens from 7075, 7475, 7050, and 7049-T7X plate has slowed to the arbitrary 10 to the -10 power m/sec used to define threshold stress intensity. Because some specimens appear to be approaching crack arrest, the importance of self-loading from corrosion product wedging as a significant driving force for crack propagation in overaged materials is questioned. Crack length-time data were analyzed using a computer curve fitting program which minimized the effects of normal data scatter, and provided a clearer picture of material performance. Precracked specimen data are supported by the results of smooth specimen tests. Transgranular stress corrosion cracking was observed in TL DCB specimens from all four alloys. This process is extremely slow and is characterized by a striated surface morphology.

Enamel coated steel reinforcement for improved durability and life-cycle performance of concrete structures: microstructure, corrosion, and deterioration

NASA Astrophysics Data System (ADS)

Tang, Fujian

This study is aimed (a) to statistically characterize the corrosion-induced deterioration process of reinforced concrete structures (concrete cracking, steel mass loss, and rebar-concrete bond degradation), and (b) to develop and apply three types of enamel-coated steel bars for improved corrosion resistance of the structures. Commercially available pure enamel, mixed enamel with 50% calcium silicate, and double enamel with an inner layer of pure enamel and an outer layer of mixed enamel were considered as various steel coatings. Electrochemical tests were respectively conducted on steel plates, smooth bars embedded in concrete, and deformed bars with/without concrete cover in 3.5 wt.% NaCl or saturated Ca(OH)2 solution. The effects of enamel microstructure, coating thickness variation, potential damage, mortar protection, and corrosion environment on corrosion resistance of the steel members were investigated. Extensive test results indicated that corrosion-induced concrete cracking can be divided into four stages that gradually become less correlated with corrosion process over time. The coefficient of variation of crack width increases with the increasing level of corrosion. Corrosion changed the cross section area instead of mechanical properties of steel bars. The bond-slip behavior between the corroded bars and concrete depends on the corrosion level and distribution of corrosion pits. Although it can improve the chemical bond with concrete and steel, the mixed enamel coating is the least corrosion resistant. The double enamel coating provides the most consistent corrosion performance and is thus recommended to coat reinforcing steel bars for concrete structures applied in corrosive environments. Corrosion pits in enamel-coated bars are limited around damage locations.

The influence of loading on the corrosion of steel in cracked ordinary Portland cement and high performance concretes

NASA Astrophysics Data System (ADS)

Jaffer, Shahzma Jafferali

Most studies that have examined chloride-induced corrosion of steel in concrete have focused on sound concrete. However, reinforced concrete is seldom uncracked and very few studies have investigated the influence of cracked concrete on rebar corrosion. Furthermore, the studies that have examined the relationship between cracks and corrosion have focused on unloaded or statically loaded cracks. However, in practice, reinforced concrete structures (e.g. bridges) are often dynamically loaded. Hence, the cracks in such structures open and close which could influence the corrosion of the reinforcing steel. Consequently, the objectives of this project were (i) to examine the effect of different types of loading on the corrosion of reinforcing steel, (ii) the influence of concrete mixture design on the corrosion behaviour and (iii) to provide data that can be used in service-life modelling of cracked reinforced concretes. In this project, cracked reinforced concrete beams made with ordinary Portland cement concrete (OPCC) and high performance concrete (HPC) were subjected to no load, static loading and dynamic loading. They were immersed in salt solution to just above the crack level at their mid-point for two weeks out of every four (wet cycle) and, for the remaining two weeks, were left in ambient laboratory conditions to dry (dry cycle). The wet cycle led to three conditions of exposure for each beam: (i) the non-submerged region, (ii) the sound, submerged region and (iii) the cracked mid-section, which was also immersed in the solution. Linear polarization resistance and galvanostatic pulse techniques were used to monitor the corrosion in the three regions. Potentiodynamic polarization, electrochemical current noise and concrete electrical resistance measurements were also performed. These measurements illustrated that (i) rebar corroded faster at cracks than in sound concrete, (ii) HPC was more protective towards the rebar than OPCC even at cracks and (iii) there was a minor effect of the type of loading on rebar corrosion within the period of the project. These measurements also highlighted the problems associated with corrosion measurements, for example, identifying the actual corroding area and the influence of the length of rebar. The numbers of cracks and crack-widths in each beam were measured after the beam's initial exposure to salt solution and, again, after the final corrosion measurements. HPC beams had more cracks than the OPCC. Also, final measurements illustrated increased crack-widths in dynamically loaded beams, regardless of the concrete type. The cracks in both statically and dynamically loaded OPCC and HPC beams bifurcated at the rebar level and propagated parallel to the rebar. This project also examined the extent of corrosion on the rebars and the distribution of corrosion products in the concrete and on the concrete walls of the cracks. Corrosion occurred only at cracks in the concrete and was spread over a larger area on the rebars in HPC than those in OPCC. The damage due to corrosion was superficial in HPC and crater-like in OPCC. Regardless of the concrete type, there was a larger distribution of corrosion products on the crack walls of the dynamically loaded beams. Corrosion products diffused into the cement paste and the paste-aggregate interface in OPCC but remained in the crack in HPC. The most voluminous corrosion product identified was ferric hydroxide. Elemental analysis of mill-scale on rebar which was not embedded in concrete or exposed to chlorides was compared to that of the bars that had been embedded in uncontaminated concrete and in cracked concrete exposed to chlorides. In uncontaminated concrete, mill-scale absorbed calcium and silicon. At a crack, a layer, composed of a mixture of cement paste and corrosion products, developed between the mill-scale and the substrate steel. Based on the results, it was concluded that (i) corrosion occurred on the rebar only at cracks in the concrete, (ii) corrosion was initiated at the cracks immediately upon exposure to salt solution, (ii) the type of loading had a minor influence on the corrosion rates of reinforcing steel and (iv) the use of polarized area led to a significant underestimation of the current density at the crack. It is recommended that the effect of cover-depth on (i) the time to initiation of corrosion and (ii) the corrosion current density in cracked concrete be investigated.

Prediction of reinforcement corrosion using corrosion induced cracks width in corroded reinforced concrete beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Inamullah; François, Raoul; Castel, Arnaud

2014-02-15

This paper studies the evolution of reinforcement corrosion in comparison to corrosion crack width in a highly corroded reinforced concrete beam. Cracking and corrosion maps of the beam were drawn and steel reinforcement was recovered from the beam to observe the corrosion pattern and to measure the loss of mass of steel reinforcement. Maximum steel cross-section loss of the main reinforcement and average steel cross-section loss between stirrups were plotted against the crack width. The experimental results were compared with existing models proposed by Rodriguez et al., Vidal et al. and Zhang et al. Time prediction models for a givenmore » opening threshold are also compared to experimental results. Steel cross-section loss for stirrups was also measured and was plotted against the crack width. It was observed that steel cross-section loss in the stirrups had no relationship with the crack width of longitudinal corrosion cracks. -- Highlights: •Relationship between crack and corrosion of reinforcement was investigated. •Corrosion results of natural process and then corresponds to in-situ conditions. •Comparison with time predicting model is provided. •Prediction of load-bearing capacity from crack pattern was studied.« less

Effect of crack openings on carbonation-induced corrosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghantous, Rita Maria, E-mail: rita-maria.ghantous@yncrea.fr; LMDC, Université de Toulouse, INSA, UPS, Toulouse; Poyet, Stéphane

Reinforced concrete is widely used in the construction of buildings, historical monuments, infrastructures and nuclear power plants. For a variety of reasons, many concrete structures are subject to unavoidable cracks that accelerate the diffusion of atmospheric carbon dioxide to the steel/concrete interface. Carbonation at the interface induces steel corrosion that could cause the development of new cracks in the structure, a determining factor for its durability. The aim of this article is to study the effect of existing cracks on the development of carbonation-induced corrosion. The results indicate that, after the initiation phase, the corrosion kinetics decreases with time andmore » the free corrosion potential increases independently of the crack opening. In addition, the corroded zone matches the carbonated one. The interpretation of these results allows the authors to conclude that, during the corrosion process, corrosion products seal the crack and act as a barrier to oxygen and water diffusion. Consequently, the influence of crack opening on corrosion development is masked and the corrosion development is limited.« less

The Growth of Small Corrosion Fatigue Cracks in Alloy 7075

NASA Technical Reports Server (NTRS)

Piascik, Robert S.

2015-01-01

The corrosion fatigue crack growth characteristics of small (greater than 35 micrometers) surface and corner cracks in aluminum alloy 7075 is established. The early stage of crack growth is studied by performing in situ long focal length microscope (500×) crack length measurements in laboratory air and 1% sodium chloride (NaCl) environments. To quantify the "small crack effect" in the corrosive environment, the corrosion fatigue crack propagation behavior of small cracks is compared to long through-the-thickness cracks grown under identical experimental conditions. In salt water, long crack constant K(sub max) growth rates are similar to small crack da/dN.

The Growth of Small Corrosion Fatigue Cracks in Alloy 7075

NASA Technical Reports Server (NTRS)

Piascik, R. S.

2001-01-01

The corrosion fatigue crack growth characteristics of small (less than 35 microns) surface and corner cracks in aluminum alloy 7075 is established. The early stage of crack growth is studied by performing in situ long focal length microscope (500X) crack length measurements in laboratory air and 1% NaCl environments. To quantify the "small crack effect" in the corrosive environment, the corrosion fatigue crack propagation behavior of small cracks is compared to long through-the-thickness cracks grown under identical experimental conditions. In salt water, long crack constant K(sub max) growth rates are similar to small crack da/dN.

The growth of small corrosion fatigue cracks in alloy 2024

NASA Technical Reports Server (NTRS)

Piascik, Robert S.; Willard, Scott A.

1993-01-01

The corrosion fatigue crack growth characteristics of small surface and corner cracks in aluminum alloy 2024 is established. The damaging effect of salt water on the early stages of small crack growth is characterized by crack initiation at constituent particle pits, intergranular microcracking for a less than 100 micrometers, and transgranular small crack growth for a micrometer. In aqueous 1 percent NaCl and at a constant anodic potential of -700 mV(sub SCE), small cracks exhibit a factor of three increase in fatigue crack growth rates compared to laboratory air. Small cracks exhibit accelerated corrosion fatigue crack growth rates at low levels of delta-K (less than 1 MPa square root of m) below long crack delta-K (sub th). When exposed to Paris regime levels of crack tip stress intensity, small corrosion fatigue cracks exhibit growth rates similar to that observed for long cracks. Results suggest that crack closure effects influence the corrosion fatigue crack growth rates of small cracks (a less than or equal to 100 micrometers). This is evidenced by similar small and long crack growth behavior at various levels of R. Contrary to the corrosion fatigue characteristics of small cracks in high strength steels, no pronounced chemical crack length effect is observed for Al by 2024 exposed to salt water.

Controlling stress corrosion cracking in mechanism components of ground support equipment

NASA Technical Reports Server (NTRS)

Majid, W. A.

1988-01-01

The selection of materials for mechanism components used in ground support equipment so that failures resulting from stress corrosion cracking will be prevented is described. A general criteria to be used in designing for resistance to stress corrosion cracking is also provided. Stress corrosion can be defined as combined action of sustained tensile stress and corrosion to cause premature failure of materials. Various aluminum, steels, nickel, titanium and copper alloys, and tempers and corrosive environment are evaluated for stress corrosion cracking.

Effect of solution treatment on stress corrosion cracking behavior of an as-forged Mg-Zn-Y-Zr alloy

PubMed Central

Wang, S. D.; Xu, D. K.; Wang, B. J.; Sheng, L. Y.; Han, E. H.; Dong, C.

2016-01-01

Effect of solid solution treatment (T4) on stress corrosion cracking (SCC) behavior of an as-forged Mg-6.7%Zn-1.3%Y-0.6%Zr (in wt.%) alloy has been investigated using slow strain rate tensile (SSRT) testing in 3.5 wt.% NaCl solution. The results demonstrated that the SCC susceptibility index (ISCC) of as-forged samples was 0.95 and its elongation-to-failure (εf) was only 1.1%. After T4 treatment, the SCC resistance was remarkably improved. The ISCC and εf values of T4 samples were 0.86 and 3.4%, respectively. Fractography and surface observation indicated that the stress corrosion cracking mode for as-forged samples was dominated by transgranular and partially intergranular morphology, whereas the cracking mode for T4 samples was transgranular. In both cases, the main cracking mechanism was associated with hydrogen embrittlement (HE). Through alleviating the corrosion attack of Mg matrix, the influence of HE on the SCC resistance of T4 samples can be greatly suppressed. PMID:27387817

Microstructure Instability of Candidate Fuel Cladding Alloys: Corrosion and Stress Corrosion Cracking Implications

NASA Astrophysics Data System (ADS)

Jiao, Yinan; Zheng, Wenyue; Guzonas, David; Kish, Joseph

2016-02-01

This paper addresses some of the overarching aspects of microstructure instability expected from both high temperature and radiation exposure that could affect the corrosion and stress corrosion cracking (SCC) resistance of the candidate austenitic Fe-Cr-Ni alloys being considered for the fuel cladding of the Canadian supercritical water-cooled reactor (SCWR) concept. An overview of the microstructure instability expected by both exposures is presented prior to turning the focus onto the implications of such instability on the corrosion and SCC resistance. Results from testing conducted using pre-treated (thermally-aged) Type 310S stainless steel to shed some light on this important issue are included to help identify the outstanding corrosion resistance assessment needs.

Aqueous stress-corrosion cracking of high-toughness D6AC steel

NASA Technical Reports Server (NTRS)

Gilbreath, W. P.; Adamson, M. J.

1976-01-01

The crack growth behavior of D6AC steel as a function of stress intensity, stress and corrosion history, and test technique, under sustained load in filtered natural seawater, 3.3 per cent sodium chloride solution, and distilled water, was investigated. Reported investigations of D6AC were considered in terms of the present study with emphasis on thermal treatment, specimen configuration, fracture toughness, crack-growth rates, initiation period, and threshold. Both threshold and growth kinetics were found to be relatively insensitive to these test parameters. The apparent incubation period was dependent on technique, both detection sensitivity and precracking stress intensity level.

Investigation of smooth specimen scc test procedures; variations in environment, specimen size, stressing frame, and stress state. [for high strength aluminum alloys

NASA Technical Reports Server (NTRS)

Lifka, B. W.; Sprowls, D. O.; Kelsey, R. A.

1975-01-01

The variables studied in the stress-corrosion cracking performance of high strength aluminum alloys were: (1) corrosiveness of the environment, (2) specimen size and stiffness of the stressing system, (3) interpretation of transgranular cracking, and (4) interaction of the state of stress and specimen orientation in a product with an anisotropic grain structure. It was shown that the probability of failure and time to fracture for a specimen loaded in direct tension are influenced by corrosion pattern, the stressing assembly stiffness, and the notch tensile strength of the alloy. Results demonstrate that the combination of a normal tension stress and a shear stress acting on the plane of maximum susceptibility in a product with a highly directional grain cause the greatest tendency for stress-corrosion cracking.

Corrosion Susceptibility of AA5083-H116 in Biologically Active Atmospheric Marine Environments

DTIC Science & Technology

2014-03-01

by the standardized nitric acid test ASTM G67." Fatigue and stress corrosion cracking behaviors of sensitized AA5083 have also been evaluated.1213... acid (NAMLT Test)," ASTM Hanbook 3.02 Corrosion of Metals; Wear and Erosion. ASTM Hanbook 3.02 Corrosion of Metals; Wear and Erosion (ASTM...DATE (DD-MM-YYYY) 12-05-2014 REPORT TYPE Conference Proceeding (refereed) 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Corrosion

Fatigue crack growth rates in a pressure vessel steel under various conditions of loading and the environment

NASA Astrophysics Data System (ADS)

Hicks, P. D.; Robinson, F. P. A.

1986-10-01

Corrosion fatigue (CF) tests have been carried out on SA508 Cl 3 pressure vessel steel, in simulated P.W.R. environments. The test variables investigated included air and P.W.R. water environments, frequency variation over the range 1 Hz to 10 Hz, transverse and longitudinal crack growth directions, temperatures of 20 °C and 50 °C, and R-ratios of 0.2 and 0.7. It was found that decreasing the test frequency increased fatigue crack growth rates (FCGR) in P.W.R. environments, P.W.R. environment testing gave enhanced crack growth (vs air tests), FCGRs were greater for cracks growing in the longitudinal direction, slight increases in temperature gave noticeable accelerations in FCGR, and several air tests gave FCGR greater than those predicted by the existing ASME codes. Fractographic evidence indicates that FCGRs were accelerated by a hydrogen embrittlement mechanism. The presence of elongated MnS inclusions aided both mechanical fatigue and hydrogen embrittlement processes, thus producing synergistically fast FCGRs. Both anodic dissolution and hydrogen embrittlement mechanisms have been proposed for the environmental enhancement of crack growth rates. Electrochemical potential measurements and potentiostatic tests have shown that sample isolation of the test specimens from the clevises in the apparatus is not essential during low temperature corrosion fatigue testing.

[Stress-corrosion test of TIG welded CP-Ti].

PubMed

Li, H; Wang, Y; Zhou, Z; Meng, X; Liang, Q; Zhang, X; Zhao, Y

2000-12-01

In this study TIG (Tungsten Inert Gas) welded CP-Ti were subjected to stress-corrosion test under 261 MPa in artificial saliva of 37 degrees C for 3 months. No significant difference was noted on mechanical test (P > 0.05). No color-changed and no micro-crack on the sample's surface yet. These results indicate that TIG welded CP-Ti offers excellent resistance to stress corrosion.

Cyclic Polarization Behavior of ASTM A537-Cl.1 Steel in the Vapor Space Above Simulated Waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiersma, B

2004-11-01

An assessment of the potential degradation mechanisms of Types I and II High-Level Waste (HLW) Tanks determined that pitting corrosion and stress corrosion cracking were the two most significant degradation mechanisms. Specifically, nitrate induced stress corrosion cracking was determined to be the principal degradation mechanism for the primary tank steel of non-stress relieved tanks. Controls on the solution chemistry have been in place to preclude the initiation and propagation of degradation in the tanks. However, recent experience has shown that steel not in contact with the bulk waste solution or slurry, but exposed to the ''vapor space'' above the bulkmore » waste, may be vulnerable to the initiation and propagation of degradation, including pitting and stress corrosion cracking. A program to resolve the issues associated with potential vapor space corrosion is in place. The objective of the program is to develop understanding of vapor space (VSC) and liquid/air interface (LAIC) corrosion to ensure a defensible technical basis to provide accurate corrosion evaluations with regard to vapor space and liquid/air interface corrosion (similar to current evaluations). There are several needs for a technically defensible basis with sufficient understanding to perform these evaluations. These include understanding of the (1) surface chemistry evolution, (2) corrosion response through coupon testing, and (3) mechanistic understanding through electrochemical studies. Experimentation performed in FY02 determined the potential for vapor space and liquid/air interface corrosion of ASTM A285-70 and ASTM A537-Cl.1 steels. The material surface characteristics, i.e. mill-scale, polished, were found to play a key role in the pitting response. The experimentation indicated that the potential for limited vapor space and liquid/air interface pitting exists at 1.5M nitrate solution when using chemistry controls designed to prevent stress corrosion cracking. Experimentation performed in FY03 quantified pitting rates as a function of material surface characteristics, including mill-scale and defects within the mill-scale. Testing was performed on ASTM A537-Cl.1 (normalized) steel, the material of construction of the Type III HLW tanks. The pitting rates were approximately 3 mpy for exposure above inhibited solutions, as calculated from the limited exposure times. This translates to a penetration time of 166 years for a 0.5-in tank wall provided that the pitting rate remains constant and the bulk solution chemistry is maintained within the L3 limit. The FY04 testing consisted of electrochemical testing to potentially lend insight into the surface chemistry and further understand the corrosion mechanism in the vapor space. Electrochemical testing lends insight into the corrosion processes through the determination of current potential relationships. The results of the electrochemical testing performed during FY04 are presented here.« less

Stress Corrosion Cracking Behavior of Multipass TIG-Welded AA2219 Aluminum Alloy in 3.5 wt pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Sreekumar, K.; Raja, V. S.

2012-09-01

The stress corrosion cracking (SCC) behavior of the AA2219 aluminum alloy in the single-pass (SP) and multipass (MP) welded conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using a slow-strain-rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both the BM and welded joints. The results showed that the ductility ratio ( ɛ NaCl/( ɛ air) was 0.97 and 0.96, respectively, for the BM and MP welded joint, and the same was marginally reduced to 0.9 for the SP welded joint. The fractographic examination of the failed samples revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy under all welded conditions. To understand the decrease in the ductility of the SP welded joint, preexposure SSRT followed by microstructural observations were made, which showed that the decrease in ductility ratio of the SP welded joint was caused by the electrochemical pitting that assisted the nucleation of cracks in the form of corrosion induced mechanical cracking rather than true SCC failure of the alloy. The microstructural examination and polarization tests demonstrated a clear grain boundary (GB) sensitization of the PMZ, resulting in severe galvanic corrosion of the SP weld joint, which initiated the necessary conditions for the localized corrosion and cracking along the PMZ. The absence of PMZ and a refined fusion zone (FZ) structure because of the lesser heat input and postweld heating effect improved the galvanic corrosion resistance of the MP welded joint greatly, and thus, failure occurred along the FZ.

CORROSION PROCESS IN REINFORCED CONCRETE IDENTIFIED BY ACOUSTIC EMISSION

NASA Astrophysics Data System (ADS)

Kawasaki, Yuma; Kitaura, Misuzu; Tomoda, Yuichi; Ohtsu, Masayasu

Deterioration of Reinforced Concrete (RC) due to salt attack is known as one of serious problems. Thus, development of non-destructive evaluation (NDE) techniques is important to assess the corrosion process. Reinforcement in concrete normally does not corrode because of a passive film on the surface of reinforcement. When chloride concentration at reinfo rcement exceeds the threshold level, the passive film is destroyed. Thus maintenance is desirable at an early stage. In this study, to identify the onset of corrosion and the nucleation of corrosion-induced cracking in concrete due to expansion of corrosion products, continuous acoustic emission (AE) monitoring is applied. Accelerated corrosion and cyclic wet and dry tests are performed in a laboratory. The SiGMA (Simplified Green's functions for Moment tensor Analysis) proce dure is applied to AE waveforms to clarify source kinematics of micro-cracks locations, types and orientations. Results show that the onset of corrosion and the nu cleation of corrosion-induced cracking in concrete are successfully identified. Additionally, cross-sections inside the reinforcement are observed by a scanning electron microscope (SEM). From these results, a great promise for AE techniques to monitor salt damage at an early stage in RC structures is demonstrated.

Stress corrosion crack initiation of Zircaloy-4 cladding tubes in an iodine vapor environment during creep, relaxation, and constant strain rate tests

NASA Astrophysics Data System (ADS)

Jezequel, T.; Auzoux, Q.; Le Boulch, D.; Bono, M.; Andrieu, E.; Blanc, C.; Chabretou, V.; Mozzani, N.; Rautenberg, M.

2018-02-01

During accidental power transient conditions with Pellet Cladding Interaction (PCI), the synergistic effect of the stress and strain imposed on the cladding by thermal expansion of the fuel, and corrosion by iodine released as a fission product, may lead to cladding failure by Stress Corrosion Cracking (SCC). In this study, internal pressure tests were conducted on unirradiated cold-worked stress-relieved Zircaloy-4 cladding tubes in an iodine vapor environment. The goal was to investigate the influence of loading type (constant pressure tests, constant circumferential strain rate tests, or constant circumferential strain tests) and test temperature (320, 350, or 380 °C) on iodine-induced stress corrosion cracking (I-SCC). The experimental results obtained with different loading types were consistent with each other. The apparent threshold hoop stress for I-SCC was found to be independent of the test temperature. SEM micrographs of the tested samples showed many pits distributed over the inner surface, which tended to coalesce into large pits in which a microcrack could initiate. A model for the time-to-failure of a cladding tube was developed using finite element simulations of the viscoplastic mechanical behavior of the material and a modified Kachanov's damage growth model. The times-to-failure predicted by this model are consistent with the experimental data.

Stress corrosion cracking properties of 15-5PH steel

NASA Technical Reports Server (NTRS)

Rosa, Ferdinand

1993-01-01

Unexpected occurrence of failures, due to stress corrosion cracking (SCC) of structural components, indicate a need for improved characterization of materials and more advanced analytical procedures for reliably predicting structures performance. Accordingly, the purpose of this study was to determine the stress corrosion susceptibility of 15-5PH steel over a wide range of applied strain rates in a highly corrosive environment. The selected environment for this investigation was a highly acidified sodium chloride (NaCl) aqueous solution. The selected alloy for the study was a 15-5PH steel in the H900 condition. The slow strain rate technique was selected to test the metals specimens.

76 FR 36395 - Airworthiness Directives; Piper Aircraft, Inc. Models PA-24, PA-24-250, and PA-24-260 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-22

... stabilator horn assembly or repetitive inspection of the stabilator horn assembly for corrosion or cracks with replacement of the stabilator horn assembly if any corrosion or cracks are found. This proposed AD... to detect and correct corrosion or cracks in the stabilator horn assembly. Corrosion or cracks could...

77 FR 68711 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-16

... test for indications of corrosion and damage to the bogie assembly base material, and a magnetic particle inspection for cracks, corrosion, and damage of the bogie beam. Corrective actions include...

Aqueous chloride stress corrosion cracking of titanium: A comparison with environmental hydrogen embrittlement

NASA Technical Reports Server (NTRS)

Nelson, H. G.

1973-01-01

The physical characteristics of stress corrosion cracking of titanium in an aqueous chloride environment are compared with those of embrittlement of titanium by a gaseous hydrogen environment in an effort to help contribute to the understanding of the possible role of hydrogen in the complex stress corrosion cracking process. Based on previous studies, the two forms of embrittlement are shown to be similar at low hydrogen pressures (100 N/sqm) but dissimilar at higher hydrogen pressures. In an effort to quantify this comparison, tests were conducted in an aqueous chloride solution using the same material and test techniques as had previously been employed in a gaseous hydrogen environment. The results of these tests strongly support models based on hydrogen as the embrittling species in an aqueous chloride environment. Further, it is shown that if hydrogen is the causal species, the effective hydrogen fugacity at the surface of titanium exposed to an aqueous chloride environment is equivalent to a molecular hydrogen pressure of approximately 10 N/sqm.

Thermally driven self-healing using copper nanofiber heater

NASA Astrophysics Data System (ADS)

Lee, Min Wook; Jo, Hong Seok; Yoon, Sam S.; Yarin, Alexander L.

2017-07-01

Nano-textured transparent heaters made of copper nanofibers (CuNFs) are used to facilitate accelerated self-healing of bromobutyl rubber (BIIR). The heater and BIIR layer are separately deposited on each side of a transparent flexible polyethylene terephthalate (PET) substrate. A pre-notched crack on the BIIR layer was bridged due to heating facilitated by CuNFs. In the corrosion test, a cracked BIIR layer covered a steel substrate. An accelerated self-healing of the crack due to the transparent copper nanofiber heater facilitated an anti-corrosion protective effect of the BIIR layer.

Elastomer-induced crevice corrosion and stress corrosion cracking of stainless steel heat exchanger plates in sour amine service

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hay, M.G.; Baron, J.J.; Moffat, T.A.

1996-08-01

Types S31600 and S31254 stainless steel heat exchanger plates have suffered crevice corrosion and stress corrosion cracking under gaskets in rich amine service in a sour gas plant. The gasket material, ethylene-propylene-diene monomer (EPDM), has been used successfully for many years at other sour gas plants. Laboratory testing has duplicated the corrosion observed and shown that the mechanism is synergistic sulfide-halide attack. The use of a bromine plus chlorine-activated curing system for the EPDM rubber gaskets provided the necessary halides. Laboratory testing identified some nickel-based superalloys which were resistant to this corrosion and also demonstrated that essentially halogen-free, peroxide-cured EPDMmore » gaskets do not cause attack of S31600 or S31254. The heat exchanger packs were replaced with S31600 plates and peroxide-cured EPDM gaskets having a specified total halogen concentration of 200 ppm maximum. Field operating experience has been excellent.« less

Prediction of failure pressure and leak rate of stress corrosion.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majumdar, S.; Kasza, K.; Park, J. Y.

2002-06-24

An ''equivalent rectangular crack'' approach was employed to predict rupture pressures and leak rates through laboratory generated stress corrosion cracks and steam generator tubes removed from the McGuire Nuclear Station. Specimen flaws were sized by post-test fractography in addition to a pre-test advanced eddy current technique. The predicted and observed test data on rupture and leak rate are compared. In general, the test failure pressures and leak rates are closer to those predicted on the basis of fractography than on nondestructive evaluation (NDE). However, the predictions based on NDE results are encouraging, particularly because they have the potential to determinemore » a more detailed geometry of ligamented cracks, from which failure pressure and leak rate can be more accurately predicted. One test specimen displayed a time-dependent increase of leak rate under constant pressure.« less

Stress corrosion crack initiation of alloy 600 in PWR primary water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Ziqing; Toloczko, Mychailo B.; Olszta, Matthew J.

Stress corrosion crack (SCC) initiation of three mill-annealed (MA) alloy 600 heats in simulated pressurized water reactor primary water has been investigated using constant load tests equipped with in-situ direct current potential drop (DCPD) measurement capabilities. SCC initiation times were greatly reduced by a small amount of cold work. Shallow intergranular (IG) attack and/or cracks were found on most high-energy grain boundaries intersecting the surface with only a small fraction evolving into larger cracks and IGSCC growth. Crack depth profiles were measured and related to DCPD-detected initiation response. Processes controlling the SCC initiation in MA alloy 600 are discussed. INmore » PRESS, CORRECTED PROOF, 05/02/2017 - mfl« less

Lead induced stress corrosion cracking of Alloy 690 in high temperature water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, K.K.; Lim, J.K.; Moriya, Shinichi

1995-12-31

Recent investigations of cracked steam generator tubes at nuclear power plants concluded that lead significantly contributed to cracking the Alloy 600 materials. In order to investigate the stress corrosion cracking (SCC) behavior of Alloy 690, slow strain rate tests (SSRT) and anodic polarization measurements were performed. The SSRTs were conducted in a lead-chloride solution (PbCl{sub 2}) and in a chloride but lead free solution (NaCl) at pH of 3 and 4.5 at 288 C. The anodic polarization measurements were carried out at 30 C using the same solutions as in SSRT. The SSRT results showed that Alloy 690 was susceptiblemore » to SCC in both solutions. In the lead chloride solution, cracking had slight dependence on lead concentration and pH. Cracking tend to increase with a higher lead concentration and a lower pH and was mainly intergranular and was to be a few tens to hundreds micrometers in length. In the chloride only solution, cracking was similar to the lead induced SCC. The results of anodic polarization measurement and electron probe micro analysis (EPMA) helped to understand lead induced SCC. Lead was a stronger active corrosive element but had a minor affect on cracking susceptibility of the alloy. While, chloride was quite different from lead effect to SCC. A possible mechanism of lead induced SCC of Alloy 690 was also discussed based on the test results.« less

The Effect of High Temperature Corrosion on Mechanical Behavior of a GAMMA-TiAl Alloy

NASA Astrophysics Data System (ADS)

Zhao, Wenyue; Ma, Yue; Gong, Shengkai

The mechanical properties of Ti-48Al-2Cr-2Nb alloy were discussed after the high temperature corrosion tests carried out with salt mixture of 75wt. % Na2SO4 and 25wt. % NaCl at 800°C. The microstructure of the alloy after corrosion was observed by SEM and the fracture behavior of the corroded and uncorroded alloys was investigated by means of the three-point bending tests. It has been shown that the corrosion path was mainly along the lamellar structure and rough surface with a large number of corrosion pits formed during the high temperature corrosion. The experimental results also indicated that the bearing capacity of bending fracture descended evidently due to the molten salt corrosion at high temperature, which only had remarkable effects on the surface state of the alloy. The microcracks inside the alloy always propagated along the phase interfaces and grain boundaries while the corrosion pits on salt-deposited surface became the main crack initiation location in corroded alloy. The stress concentration caused by corrosion was considered as the essential reason of the property reduction, which decreased the energy barrier of crack nucleation and shortened the incubation period.

Caustic stress corrosion cracking of alloys 600 and 690 with NaOH concentrations

NASA Astrophysics Data System (ADS)

Park, In-Gyu; Lee, Chang-Soon; Hwang, Seong-Sik; Kim, Hong-Pyo; Kim, Joung-Soo

2005-10-01

In order to evaluate the stress corrosion cracking resistance for commercial alloys (C600MA, C600TT, C690TT) and Korean-made alloys (K600MA, K690TT), C-ring tests were performed in a caustic environment of 4, 10, 20, 30, and 50% NaOH solution at 315°C, for 480 h with an applied potential of 125 mV vs. OCP. Different stress corrosion cracking phenomena were observed according to the NaOH concentration. The rate of caustic IGSCC attack did not appear to increase monotonically with caustic concentrations, but peaked at a concentration between 4 and 50% caustic, or approximately 30% NaOH. Intergranular stress corrosion cracking was found for C600MA in 10, 20, and 30% NaOH solutions, while no cracking was observed in the 4 and 50% NaOH solutions. In 30% NaOH solution, transgrnular stress corrosion cracking was detected in C690TT, which may be related with the large amount of plastic strain (150% yield) and the applied potential (125 mV vs. OCP). The overall data clearly indicate that C600MA has the worst SCC resistance while K690TT offers the best resistance. There is also fairly good correlation between the caustic SCC susceptibility and some metallurgical parameters, particularly the grain size and the yield strength at room temperature. Specifically, materials having larger grain size and lower yield strength exhibited higher caustic SCC resistance.

Materials screening tests for the krypton-85 storage development program

NASA Astrophysics Data System (ADS)

Nagata, P. K.

1981-04-01

The results of a materials testing program for krypton-85 storage techniques are reported. Corrosion and stress corrosion tests were performed on a variety of materials including AISI 4130, Type 316 SS, Type 304 SS, Type 310 SS, Nitronic 50, and alloy A286. Test environments were high-purity liquid rubidium, liquid rubidium contaminated with oxygen, and rubidium hydroxide. Oxygen and water contaminations in liquid rubidium were found to greatly increase both general and localized corrosion of the materials tested. Alloy A286, Type 304 SS, and AISI 4130 were eliminated as candidate materials due to their susceptibility to general corrosion and stress corrosion cracking.

Precursor Evolution and Stress Corrosion Cracking Initiation of Cold-Worked Alloy 690 in Simulated Pressurized Water Reactor Primary Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Ziqing; Toloczko, Mychailo; Kruska, Karen

Stress corrosion crack initiation of two thermally-treated, cold-worked (CW) alloy 690 (UNS N06690) materials was investigated in 360oC simulated PWR primary water using constant load tensile (CLT) tests and blunt notch compact tension (BNCT) tests equipped with direct current potential drop (DCPD) for in-situ detection of cracking. SCC initiation was not detected by DCPD for either the 21% or 31%CW CLT specimens loaded at their yield stress after ~9,220 hours, however intergranular (IG) precursor damage and isolated surface cracks were observed on the specimens. The two 31%CW BNCT specimens loaded at moderate stress intensity after several cyclic loading ramps showedmore » DCPD-indicated crack initiation after 10,400 hours of exposure at constant stress intensity, which was resulted from significant growth of IG cracks. The 21%CW BNCT specimens only exhibited isolated small IG surface cracks and showed no apparent DCPD change throughout the test. Post-test cross-section examinations revealed many grain boundary (GB) nano-cavities in the bulk of all the CLT and BNCT specimens particularly for the 31%CW materials. Cavities were also found along GBs extending to the surface suggesting an important role in crack nucleation. This paper provides an overview of the evolution of GB cavities and discusses their effects on crack initiation in CW alloy 690.« less

Corrosion and stress corrosion cracking of ferritic/martensitic steel in super critical pressurized water

NASA Astrophysics Data System (ADS)

Hirose, T.; Shiba, K.; Enoeda, M.; Akiba, M.

2007-08-01

A water-cooled solid breeder (WCSB) blanket cooled by high temperature SCPW (super critical pressurized water) is a practical option of DEMO reactor. Therefore, it is necessary to check the compatibility of the steel with SCPW. In this work, reduced activation ferritic/martensitic steel, F82H has been tested through slow strain rate tests (SSRT) in 23.5 MPa SCPW. And weight change behavior was measured up to 1000 h. F82H did not demonstrated stress corrosion cracking and its weight simply increased with surface oxidation. The weight change of F82H was almost same as commercial 9%-Cr steels. According to a cross-sectional analysis and weight change behavior, corrosion rate of F82H in the 823 K SCPW is estimated to be 0.04 mm/yr.

Hydrogen assisted cracking and CO2 corrosion behaviors of low-alloy steel with high strength used for armor layer of flexible pipe

NASA Astrophysics Data System (ADS)

Liu, Zhenguang; Gao, Xiuhua; Du, Linxiu; Li, Jianping; Zhou, Xiaowei; Wang, Xiaonan; Wang, Yuxin; Liu, Chuan; Xu, Guoxiang; Misra, R. D. K.

2018-05-01

In this study, hydrogen induced cracking (HIC), sulfide stress corrosion cracking (SSCC) and hydrogen embrittlement (HE) were carried out to study hydrogen assisted cracking behavior (HIC, SSCC and HE) of high strength pipeline steel used for armor layer of flexible pipe in ocean. The CO2 corrosion behavior of designed steel with high strength was studied by using immersion experiment. The experimental results demonstrate that the corrosion resistance of designed steel with tempered martensite to HIC, SSCC and HE is excellent according to specific standards, which contributes to the low concentration of dislocation and vacancies previously formed in cold rolling process. The corrosion mechanism of hydrogen induced cracking of designed steel, which involves in producing process, microstructure and cracking behavior, is proposed. The designed steel with tempered martensite shows excellent corrosion resistance to CO2 corrosion. Cr-rich compound was first formed on the coupon surface exposed to CO2-saturated brine condition and chlorine, one of the corrosion ions in solution, was rich in the inner layer of corrosion products.

Stress corrosion cracking of duplex stainless steels in caustic solutions

NASA Astrophysics Data System (ADS)

Bhattacharya, Ananya

Duplex stainless steels (DSS) with roughly equal amount of austenite and ferrite phases are being used in industries such as petrochemical, nuclear, pulp and paper mills, de-salination plants, marine environments, and others. However, many DSS grades have been reported to undergo corrosion and stress corrosion cracking in some aggressive environments such as chlorides and sulfide-containing caustic solutions. Although stress corrosion cracking of duplex stainless steels in chloride solution has been investigated and well documented in the literature but the SCC mechanisms for DSS in caustic solutions were not known. Microstructural changes during fabrication processes affect the overall SCC susceptibility of these steels in caustic solutions. Other environmental factors, like pH of the solution, temperature, and resulting electrochemical potential also influence the SCC susceptibility of duplex stainless steels. In this study, the role of material and environmental parameters on corrosion and stress corrosion cracking of duplex stainless steels in caustic solutions were investigated. Changes in the DSS microstructure by different annealing and aging treatments were characterized in terms of changes in the ratio of austenite and ferrite phases, phase morphology and intermetallic precipitation using optical micrography, SEM, EDS, XRD, nano-indentation and microhardness methods. These samples were then tested for general and localized corrosion susceptibility and SCC to understand the underlying mechanisms of crack initiation and propagation in DSS in the above-mentioned environments. Results showed that the austenite phase in the DSS is more susceptible to crack initiation and propagation in caustic solutions, which is different from that in the low pH chloride environment where the ferrite phase is the more susceptible phase. This study also showed that microstructural changes in duplex stainless steels due to different heat treatments could affect their SCC susceptibility. Annealed and water quenched specimens were found to be immune to SCC in caustic environment. Aging treatment at 800°C gave rise to sigma and chi precipitates in the DSS. However, these sigma and chi precipitates, known to initiate cracking in DSS in chloride environment did not cause any cracking of DSS in caustic solutions. Aging of DSS at 475°C had resulted in '475°C embrittlement' and caused cracks to initiate in the ferrite phase. This was in contrast to the cracks initiating in the austenite phase in the as-received DSS. Alloy composition and microstructure of DSS as well as solution composition (dissolved ionic species) was also found to affect the electrochemical behavior and passivation of DSS which in turn plays a major role in stress corrosion crack initiation and propagation. Corrosion rates and SCC susceptibility of DSS was found to increase with addition of sulfide to caustic solutions. Corrosion films on DSS, characterized using XRD and X-ray photoelectron spectroscopy, indicated that the metal sulfide compounds were formed along with oxides at the metal surface in the presence of sulfide containing caustic environments. These metal sulfide containing passive films are unstable and hence breaks down under mechanical straining, leading to SCC initiations. The overall results from this study helped in understanding the mechanism of SCC in caustic solutions. Favorable slip systems in the austenite phase of DSS favors slip-induced local film damage thereby initiating a stress corrosion crack. Repeated film repassivation and breaking, followed by crack tip dissolution results in crack propagation in the austenite phase of DSS alloys. Result from this study will have a significant impact in terms of identifying the alloy compositions, fabrication processes, microstructures, and environmental conditions that may be avoided to mitigate corrosion and stress corrosion cracking of DSS in caustic solutions.

Investigation of corrosion and stress corrosion cracking susceptibility of S30400 and S31600 stainless steels exposed to commercial soldering flux containing zinc chloride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, D.T.

1995-10-01

A corrosion investigation was conducted to determine corrosion behavior and stress corrosion cracking (SCC) susceptibility of S30400 and S31600 stainless steel exposed to soldering flux paste containing 25 wt% zinc chloride. Electrochemical test results indicated that soldering flux paste was not corrosive to S30400 and S31600 at room temperature. The wax phase (light phase) of soldering flux was also not corrosive to S30400 and S31600. However, the heavy phase of solder flux was corrosive to S30400 and S31600 at elevated temperatures. In heavy phase, S30400 did not passivate, while S31600 passivated at temperatures up to 80 C while no passivitymore » was observed at 85 C and above. AC impedance test results showed that S30400 and S31600 corroded at rates of less than 0.1 mpy in solder flux pastes at room temperature. In the soldering flux heavy phase, corrosion rates were about 2 mpy or less for S30400 at temperatures up to 75 C and S31600 at temperatures up to 70 C. However, corrosion rates of S30400 in the soldering flux heavy phase increased to 5, 8, 10, and 22 mpy at 80, 85, 90, and 95 C while corrosion rates of S31600 sst in the soldering flux heavy phase increased to 4, 5, 7, and 11, and 30 mpy at 75, 80, 85, 90 and 95 C, respectively. CERT results revealed that no SCC susceptibility when S30400 and S31600 were exposed to soldering flux paste at room temperature and wax phase at 65 and 95 C. However, both test alloys were susceptible to transgranular SCC when exposed to the soldering flux heavy phase at temperatures of 65+ C. Severity of SCC increased with temperature increase. SCC fractures were characterized by reduction of ductility and numerous SCC secondary cracks on the specimen gage length. The most severe SCC fracture was observed on a S30400 specimen partially submersed in the soldering flux heavy phase and partially submersed in the soldering flux wax phase at 95 C. No similar cracking was observed on S31600.« less

Intergranular stress corrosion cracking and selective internal oxidation of nickel-chromium-iron alloys in hydrogenated steam

NASA Astrophysics Data System (ADS)

Capell, Brent M.

2005-07-01

Selective internal oxidation (SIO) is a mechanism of grain boundary embrittlement through the formation of intergranular oxides of Cr2O3. SIO is proposed as a mechanism to explain intergranular stress corrosion cracking (IGSCC) of Ni-base alloys in pressurized water reactor environments. The purpose of this work is to investigate SIO through a series of experiments using controlled-purity alloys in a controlled, low-pressure steam environment in which the oxygen potential is varied. Five alloys; Ni-9Fe, Ni-5Cr, LCr (Ni-5Cr-9Fe), CD85 (Ni-16Cr-9Fe) and HCr (Ni-30Cr-9Fe), were used in corrosion coupon exposure tests and constant extension rate tensile (CERT) tests at 550°C and 400°C in an environment consisting of a controlled mixture of hydrogen, water vapor and argon. The hydrogen-to-water vapor partial pressure ratio (PPR) was varied between 0.001 and 0.9 to control the oxygen partial pressure. The Ni-9Fe, Ni-5Cr and LCr alloys formed a uniform Ni(OH)2 film at PPR values less than 0.09 while CD85 and HCr formed Cr2O 3 oxide films over the entire PPR range. Corrosion coupon results also show the formation of highly localized oxide particles at grain boundaries. Focused ion beam analysis revealed that intergranular oxides were observed at significant depths (>150 nm) down grain boundaries and the oxide morphology depended on the alloy composition and PPR value. Diffusion of oxygen along the grain boundary accounted for the growth of intergranular oxides. CERT test results showed that intergranular cracking was caused by creep-induced microvoid coalescence only at 550°C and did not depend on PPR. At 400°C, the cracking behavior depended on the PPR and resulted in a mixture of creep-induced microvoid coalescence and brittle intergranular failure. The cracked boundary fraction was higher at a PPR value where a Ni(OH)2 surface film formed. Alloy composition influenced cracking and the cracked boundary fraction decreased as the alloy chromium content increased. The compositions of oxides at intergranular crack tips were similar to intergranular oxides in corrosion coupons and demonstrated a link between intergranular oxide formation and intergranular cracking. The observation of intergranular oxides as well as the influence of alloy content on IG cracking was found to support SIO as a mechanism for IGSCC.

EFFECT OF STRENGTHENING AT EXPECTED DAMAGING ZONE OF A RC MEMBER WITH DAMAGED ANCHORAGE

NASA Astrophysics Data System (ADS)

Chijiwa, Nobuhiro; Kawanaka, Isao; Maekawa, Koichi

When a reinforced concrete member having cracks at the anchorage zones is loaded, diagonal crack is formed from the tip of the exsisting crack, and it lead s to brittle shaer failure. A reinforced concrete beam containing corrosion cracks at the anchorage zone were strengthened with sheets at the expected damaging zones, and tested in 3-point loading. Th e test result shows that the load capacity of the strengthened beam was the same to that of the repli cate beam with no damage at the anchorage zones and contained enough shear reinforcement to develop flexural failure. It means that strenghtneing at the expected damaging zone with keeping corrosion cr acks along to the tensile reinforcements at the anchorage zones may improve the load capacity of the damaged reinforced concrete.

High-Resolution Characterizations of Grain Boundary Damage and Stress Corrosion Cracks in Cold-Rolled Alloy 690

NASA Astrophysics Data System (ADS)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.; Thomas, L. E.

Unidirectional cold rolling has been shown to promote intergranular stress corrosion cracking (IGSCC) in alloy 690 tested in PWR primary water. High-resolution scanning (SEM) and transmission electron microscopy (TEM) have been employed to investigate the microstructural reasons for this enhanced susceptibility in two stages, first examining grain boundary damage produced by cold rolling and second by characterization of stress corrosion crack tips. The degree of permanent grain boundary damage from cold rolling was found to depend directly on the initial IG precipitate distribution. Cold rolling to high levels of reduction was discovered to produce small IG voids and cracked carbides in alloys with a high density of grain boundary carbides. For the same degree of cold rolling, alloys with few IG carbides exhibited much less permanent damage. Although this difference in grain boundary damage appears to correlate with measured SCC growth rates, crack tip examinations reveal no interaction between the preexisting voids and cracked carbides with the propagation. In many cases, these features appeared to blunt propagation of IGSCC cracks. High-resolution characterizations are described for cold-rolled alloy 690 CRDM tubing and plate materials to gain insights into IGSCC mechanisms.

Evaluation of the stress corrosion cracking resistance of several high strength low alloy steels

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1980-01-01

The stress corrosion cracking resistance was studied for high strength alloy steels 4130, 4340, for H-11 at selected strength levels, and for D6AC and HY140 at a single strength. Round tensile and C-ring type specimens were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, salt spray, the atmosphere at Marshall Space Flight Center, and the seacoast at Kennedy Space Center. Under the test conditions, 4130 and 4340 steels heat treated to a tensile strength of 1240 MPa (180 ksi), H-11 and D6AC heat treated to a tensile strength of 1450 MPa (210 ksi), and HY140 (1020 MPa, 148 ksi) are resistant to stress corrosion cracking because failures were not encountered at stress levels up to 75 percent of their yield strengths. A maximum exposure period of one month for alternate immersion in salt water or salt spray and three months for seacoast is indicated for alloy steel to avoid false indications of stress corrosion cracking because of failure resulting from severe pitting.

The Test and Evaluation of a Non-Chromate Finishing Agent

NASA Technical Reports Server (NTRS)

Gulley, H.; Okhio, C. B.; Tacina, Robert (Technical Monitor)

2000-01-01

This research is focused on the design, development and implementation of an industry, military and commercial standard testing cell for surface coatings, which focuses on advanced non-chromate materials technology and their commercialization. Currently, within both private and commercial sectors, chromates are used in the corrosion prevention. processes. However, there is a great demand for chromate-free systems that are able to provide equal protection. At the end of this effort, it is intended that a patented alternative to chromate conversion coatings would be tested and processed for commercialization. Thus far, research studies have been concerned primarily with current corrosion knowledge and testing methods. Corrosion can be classified into five categories: The first type is uniform corrosion which is dominated by a uniform thinning due to an even and regular loss of metal. The second type is called localized corrosion in which most of the loss occurs in discrete areas. The third type, metallurgically influenced corrosion is a form of attack where metallurgy plays a significant role. The fourth type, titled mechanically assisted degradation is a form of attack where velocity, abrasion, and hydrodynamics control the corrosion process. The last type of corrosion is defined as environmentally induced cracking which occurs when cracks are produced under specific, premeditated stress. Oddly enough, with these varying classifications, there are not as many standardized corrosion testing sites. Two of the most common testing methods for corrosion are salt spray testing and filiform. Although neither has proven to be absolute, in terms of the resulting observations, our research aims to help provide data that may be used to support the standardization for corrosion testing. We would acquire and use a Singleton Cyclic Corrosion Testing Chamber. Singleton test chambers perform a wide range of commonly used catalytic corrosion tests. They are used throughout the industry, some of which are - automotive, aerospace, electronic and many more. In addition to this, Singleton test chambers are fully expandable to accommodate cyclic corrosion testing needs. Singleton chambers are also designed for complete compliance and conformity with ASTM (American Society for Testing and Materials), military and commercial standards.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruska, Karen; Zhai, Ziqing; Bruemmer, Stephen M.

Due to its superior resistance to corrosion and stress corrosion cracking (SCC), high Cr, Ni-base Alloy 690 is now commonly used in pressurized water reactors (PWRs). Even though highly cold-worked (CW) Alloy 690 has been shown to be susceptible to SCC crack growth in PWR primary water environments, an open question remains whether SCC initiation was possible for these materials under constant load test conditions. Testing has been performed on a series of CW alloy 690 CRDM tubing specimens at constant load for up to 9,220 hours in 360°C simulated PWR primary water. A companion paper will discuss the overallmore » testing approach and describe results on different alloy 690 heats and cold work levels. The focus of the current paper is to illustrate the use of focused ion beam (FIB), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for the high-resolution investigation of precursor damage and intergranular (IG) crack nucleation in these specimens. Three-dimensional (3D) FIB/SEM imaging has been conducted on a series of grain boundary (GB) damage precursors, such as IG small cavities, local corrosion and even shallow cracks observed at the specimen surface. Contrast variations and EDS mapping were used to distinguish oxides, carbides and cavities from the matrix material. Nanometer-sized cavities were observed associated with GB carbides in the highly CW specimens. Shallow IG cracks were present in the 30%CW specimens and exhibited oxidized crack flanks and a higher density of cavities ahead of the oxide front in all cases. The shape and distribution of carbides and cavities in the plane of the cracked GBs was analyzed in 3D to gain a mechanistic understanding of the processes that may be leading to crack initiation in highly CW alloy 690.« less

Characterization of Environmentally Assisted Cracking for Design: State of the Art.

DTIC Science & Technology

1982-01-01

Barsom, J.M., Effect of cyclic stress form on corrosion fatigue crack propagation below Kiscc in a high yield strength steel , in Corrosion Fatigue... Effect of Prestressing on the Stress Corrosion Resistance of Two High Strength Steels , Boeing Document D6-25275, Boeing Company, Seattle, Washington...sT’e Residual stress Crack growth High strength steel Seawater Crack initiation Hydrogen embrittlement Stress corrosion Design Linear elastic fracture

Multiple corrosion protection systems for reinforced concrete bridge components.

DOT National Transportation Integrated Search

2007-07-01

Eleven systems combining epoxy-coated reinforcement with another corrosion protection system are evaluated using : the rapid macrocell, Southern Exposure, cracked beam, and linear polarization resistance tests. The systems include : bars that are pre...

Effect of Repair Welding on Electrochemical Corrosion and Stress Corrosion Cracking Behavior of TIG Welded AA2219 Aluminum Alloy in 3.5 Wt Pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Sreekumar, K.; Raja, V. S.

2010-12-01

The stress corrosion cracking (SCC) behavior of AA2219 aluminum alloy in the as-welded (AW) and repair-welded (RW) conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using the slow strain rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both BM and welded joints. The results show that the ductility ratio ( ɛ NaCl/( ɛ air)) of the BM was close to one (0.97) and reduced to 0.9 for the AW joint. This value further reduced to 0.77 after carrying out one repair welding operation. However, the RW specimen exhibited higher ductility than the single-weld specimens even in 3.5 wt pct NaCl solution. SSRT results obtained using pre-exposed samples followed by post-test metallographic observations clearly showed localized pitting corrosion along the partially melted zone (PMZ), signifying that the reduction in ductility ratio of both the AW and RW joints was more due to mechanical overload failure, caused by the localized corrosion and a consequent reduction in specimen thickness, than due to SCC. Also, the RW joint exhibited higher ductility than the AW joint both in air and the environment, although SCC index (SI) for the former is lower than that of the latter. Fractographic examination of the failed samples, in general, revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy. Microstructural examination and polarization tests further demonstrate grain boundary melting along the PMZ, and that provided the necessary electrochemical condition for the preferential cracking on that zone of the weldment.

Corrosion Assessment of Candidate Materials for the SHINE Subcritical Assembly Vessel and Components FY15 Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J.

2016-01-01

In the previous report of this series, a literature review was performed to assess the potential for substantial corrosion issues associated with the proposed SHINE process conditions to produce 99Mo. Following the initial review, substantial laboratory corrosion testing was performed emphasizing immersion and vapor-phase exposure of candidate alloys in a wide variety of solution chemistries and temperatures representative of potential exposure conditions. Stress corrosion cracking was not identified in any of the exposures up to 10 days at 80°C and 10 additional days at 93°C. Mechanical properties and specimen fracture face features resulting from slow-strain rate tests further supported amore » lack of sensitivity of these alloys to stress corrosion cracking. Fluid velocity was found not to be an important variable (0 to ~3 m/s) in the corrosion of candidate alloys at room temperature and 50°C. Uranium in solution was not found to adversely influence potential erosion-corrosion. Potentially intense radiolysis conditions slightly accelerated the general corrosion of candidate alloys, but no materials were observed to exhibit an annualized rate above 10 μm/y.« less

STRESS CORROSION CRACK GROWTH RESPONSE FOR ALLOY 152/52 DISSIMILAR METAL WELDS IN PWR PRIMARY WATER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toloczko, Mychailo B.; Olszta, Matthew J.; Overman, Nicole R.

2015-08-15

As part of ongoing research into primary water stress corrosion cracking (PWSCC) susceptibility of alloy 690 and its welds, SCC tests have been conducted on alloy 152/52 dissimilar metal (DM) welds with cracks positioned with the goal to assess weld dilution and fusion line effects on SCC susceptibility. No increased crack growth rate was found when evaluating a 20% Cr dilution zone in alloy 152M joined to carbon steel (CS) that had not undergone a post-weld heat treatment (PWHT). However, high SCC crack growth rates were observed when the crack reached the fusion line of that material where it propagatedmore » both on the fusion line and in the heat affected zone (HAZ) of the carbon steel. Crack surface and crack profile examinations of the specimen revealed that cracking in the weld region was transgranular (TG) with weld grain boundaries not aligned with the geometric crack growth plane of the specimen. The application of a typical pressure vessel PWHT on a second set of alloy 152/52 – carbon steel DM weld specimens was found to eliminate the high SCC susceptibility in the fusion line and carbon steel HAZ regions. PWSCC tests were also performed on alloy 152-304SS DM weld specimens. Constant K crack growth rates did not exceed 5x10-9 mm/s in this material with post-test examinations revealing cracking primarily on the fusion line and slightly into the 304SS HAZ.« less

Resistance of Some Steels to Stress Corrosion Cracking

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1982-01-01

Evaluations of stress-corrosion cracking resistance of five high-strength low-alloy steels described in report now available. Steels were heat-treated to various tensile strengths and found to be highly resistant to stress-corrosion cracking.

Characterization of Stress Corrosion Cracking Using Laser Ultrasonics

DOT National Transportation Integrated Search

2007-02-15

Stress Corrosion Cracking (SCC) is a phenomenon where metals, when subjected to a combination of suitable loads, corrosive environment and susceptible metallurgy, develop crack-clusters that may lead to a failure. Pipeline systems all-over the world ...

Effect of chloride contamination in MON-1 propellant on crack growth properties of metals

NASA Technical Reports Server (NTRS)

Moran, C. M.; Toth, L. R.

1981-01-01

The effect of a high level of chloride content (800 ppm) in MON-1 propellant on the crack growth properties of seven materials was investigated. Sustained load tests were conducted at 49 C (120 F) temperature with thin gauge tensile specimens having a semi-elliptical surface flaw. Alloys included aluminum 1100, 3003, 5086 and 6061; corrosion resistant steel types A286 and 347; and titanium 6Al-4V. The configurations tested with precracked flaws exposed to MON-1 were: parent or base metal, center weld, and heat affected zone. It was concluded that this chloride level in MON-1 does not affect the stress corrosion, crack growth properties of these alloys after 1000 hour exposure duration under high stresses.

Structure, chemistry, and stress corrosion cracking of grain boundaries in alloys 600 and 690

NASA Astrophysics Data System (ADS)

Stiller, Krystyna; Nilsson, Jan-Olof; Norring, Kjell

1996-02-01

The microstructure in six commercial batches of alloys 600 and 690 has been investigated using scanning electron microscopy (SEM), analytical transmission electron microscopy (ATEM), atom probe field ion microscopy (APFIM), and secondary ion mass spectroscopy (SIMS). The materials were also tested with respect to their resistance to intergranular stress corrosion cracking (IGSCC) in high-purity water at 365 °. Applied microanalytical techniques allowed direct measurement of carbon concentration in the matrix together with determination of grain boundary micro structure and microchemistry in all material conditions. The distribution of oxygen near a crack in material tested with respect to IGSCC was also investigated. The role of carbon and chromium and intergranular precipitates on IGSCC is discussed.

Strain corrosion cracking in rpm sewer piping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopkins, S.W.; Wachob, H.F.; Duffner, D.H.

1993-12-31

Long term, aggressive environmental exposure can result in localized failure of large diameter, glass reinforced plastic mortar (RPM) piping. In order to evaluate the performance of the liner and glass reinforced matrix polyester resin, accelerated strain corrosion tests were performed on samples of RPM piping that had already experienced almost 15 years of service. To assess the sensitivity of RPM pipe to acidic environments and to correlate the fractography of the laboratory produced failures with the excavated crack, short segments of 8-inch and 48-inch diameter piping were statically loaded to produce various known surface strains. After preloading the specimens tomore » fixed strain levels, these samples were then exposed to sulfuric acid solutions having pH values of 2.7 and 4.7 and monitored as a function of time until failure. The resulting lifetimes were related to initial surface strains and showed a decreasing logarithmic relationship. Fractographic examination of the excavated crack revealed the typical strain corrosion fractography of glass fibers after almost a 1000 hour exposure at 1.3 % strain; similar fractographic observations were obtained from failed laboratory samples. At shorter times, failure appeared to be overload in nature and exhibited little, if any, timedependent fracture features. Fractographic examination of the excavated crack strongly indicated that the crack had been present for a significant time. The extremely aggressive environment had totally dissolved the exposed glass reinforcement. Based on the laboratory strain corrosion performance, the nature of the contained cracking, and fractography of the failed surface, cracking of the excavated RPM pipe was believed to be the result of an early overload failure that subsequently propagated slowly via strain corrosion in an extremely aggressive environment.« less

Investigation of the weldability of iron-aluminum-chromium overlay coatings for corrosion protection in oxidizing/sulfidizing environments

NASA Astrophysics Data System (ADS)

Regina, Jonathan R.

The current study investigated the effect of chromium additions on the hydrogen cracking susceptibility of Fe-Al weld overlay claddings containing chromium additions. It was found that the weldability of FeAlCr claddings was a function of both the aluminum and chromium concentrations of the weld coatings. Weld overlay compositions that were not susceptible to hydrogen cracking were identified and the underlying mechanism behind the hydrogen cracking phenomenon was investigated further. It was concluded that the cracking behavior of the FeAlCr welds depended strongly on the microstructure of the weld fusion zone. Although it was found that the cracking susceptibility was influenced by the presence of Fe-Al intermetallic phases (namely Fe3 Al and FeAl), the cracking behavior of FeAlCr weld overlay claddings also depended on the size and distribution of carbide and oxide particles present within the weld structure. These particles acted as hydrogen trapping sites, which are areas where free hydrogen segregates and can no longer contribute to the hydrogen embrittlement of the metal. It was determined that in practical applications of these FeAlCr weld overlay coatings, carbon should be present within these welds to reduce the amount of hydrogen available for hydrogen cracking. Based on the weldability results of the FeAlCr weld claddings, coating compositions that were able to be deposited crack-free were used for long-term corrosion testing in a simulated low NOx environment. These alloys were compared to a Ni-based superalloy (622), which is commonly utilized as boiler tube coatings in power plant furnaces for corrosion protection. It was found that the FeAlCr alloys demonstrated superior corrosion resistance when compared to the Ni-based superalloy. Due to the excellent long-term corrosion behavior of FeAlCr weld overlays that were immune to hydrogen cracking, it was concluded that select FeAlCr weld overlay compositions would make excellent corrosion resistant coatings for boiler tubes located in low NOx burning environments.

One Dimensional Cold Rolling Effects on Stress Corrosion Crack Growth in Alloy 690 Tubing and Plate Materials

NASA Astrophysics Data System (ADS)

Toloczko, Mychailo B.; Olszta, Matthew J.; Bruemmer, Stephen M.

Stress corrosion crack-growth experiments have been performed on cold-rolled alloy 690 materials in simulated PWR primary water at 360°C. Extruded alloy 690 CRDM tubing in two conditions, thermally treated (TT) and solution annealed (SA), was cold rolled (CR) in one direction to several reductions reaching a maximum of 31% and tested in the S-L orientation. High stress corrosion cracking (SCC) propagation rates ( 8x10-8 mm/s) were observed for the 31%CR alloy 690TT material, while the 31%CR alloy 690SA exhibited 10X lower rates. The difference in intergranular SCC susceptibility appears to be related to grain boundary carbide distribution before cold rolling. SCC growth rates were found to depend on test temperature and hydrogen concentration. Tests were also performed on two alloy 690 plate heats, one CR to a reduction of 26% and the other to 20%. SCC growth rates at 360°C were similar to that measured for the 31%CR alloy 690TT CRDM tubing. Comparisons will be made to other results on CR alloy 690 materials.

Pitting and Stress Corrosion Cracking Susceptibility of Nanostructured Al-Mg Alloys in Natural and Artificial Environments

NASA Astrophysics Data System (ADS)

Sharma, Mala M.; Ziemian, Constance W.

2008-12-01

The stress corrosion cracking (SCC) behavior of two developmental nanocrystalline 5083 alloys with varied composition and processing conditions was studied. The results were compared to a commercial aluminum AA 5083 (H111) alloy. The pitting densities, size and depths, and residual tensile strengths were measured after alternate immersion in artificial seawater and atmospheric exposure under different loading conditions. Optical and scanning electron microscopy (SEM) with EDX was used to analyze the fracture surfaces of failed specimen after removal at selected intervals and tensile testing. One of the nanostructured Al-Mg alloys exhibited significantly superior pitting resistance when compared to conventional microstructured AA 5083. Under conditions where pitting corrosion showed up as local tunnels toward phase inclusions, transgranular cracking was observed, whereas under conditions when pitting corrosion evolved along grain boundaries, intergranular cracking inside the pit was observed. Pit initiation resistance of the nano alloys appears to be better than that of the conventional alloys. However, long-term pit propagation is a concern and warrants further study. The objective of this investigation was to obtain information regarding the role that ultra-fine microstructures play in their degradation in marine environments and to provide insight into the corrosion mechanisms and damage processes of these alloys.

Damage assessment in PRC and RC beams by dynamic tests

NASA Astrophysics Data System (ADS)

Capozucca, R.

2011-07-01

The present paper reports on damaged prestressed reinforced concrete (PRC) beams and reinforced concrete (RC) beams experimentally investigated through dynamic testing in order to verify damage degree due to reinforcement corrosion or cracking correlated to loading. The experimental program foresaw that PRC beams were subjected to artificial reinforcement corrosion and static loading while RC beams were damaged by increasing applied loads to produce bending cracking. Dynamic investigation was developed both on undamaged and damaged PRC and RC beams measuring natural frequencies and evaluating vibration mode shapes. Dynamic testing allowed the recording of frequency response variations at different vibration modes. The experimental results are compared with theoretical results and discussed.

Crack Initiation and Growth Behavior at Corrosion Pit in 7075-T6 High Strength Aluminum Alloy

DTIC Science & Technology

2013-06-01

Corrosion Fatigue Corrosion fatigue is defined as the failure of metal due to a cyclical load in combination with exposure to a caustic environment...lifetime is spent creating the crack while the actual crack growth makes up a smaller portion of the total lifetime. With corrosion fatigue however

Simulation of Fatigue Crack Initiation at Corrosion Pits With EDM Notches

NASA Technical Reports Server (NTRS)

Smith, Stephen W.; Newman, John A.; Piascik, Robert S.

2003-01-01

Uniaxial fatigue tests were conducted to compare the fatigue life of laboratory produced corrosion pits, similar to those observed in the shuttle main landing gear wheel bolt-hole, and an electro-discharged-machined (EDM) flaw. EDM Jaws are used to simulate corrosion pits during shuttle wheel (dynamometer) testing. The aluminum alloy, (AA 7050) laboratory fatigue tests were conducted to simulate the local stress level contained in the wheel bolt-hole. Under this high local stress condition, the EDM notch produced a fatigue life similar to test specimens containing corrosion pits of similar size. Based on the laboratory fatigue test results, the EDM Jaw (semi-circular disc shaped) produces a local stress state similar to corrosion pits and can be used to simulate a corrosion pit during the shuttle wheel dynamometer tests.

Effect of ferrite transformation on the tensile and stress corrosion properties of type 316 L stainless steel weld metal thermally aged at 873 K

NASA Astrophysics Data System (ADS)

Shaikh, H.; Khatak, H. S.; Seshadri, S. K.; Gnanamoorthy, J. B.; Rodriguez, P.

1995-07-01

This article deals with the effect of the microstructural changes, due to transformation of delta ferrite, on the associated variations that take place in the tensile and stress corrosion properties of type 316 L stainless steel weld deposits when subjected to postweld heat treatment at 873 K for prolonged periods (up to 2000 hours). On aging for short durations (up to 20 hours), carbide/ carbonitride was the dominant transformation product, whereas sigma phase was dominant at longer aging times. The changes in the tensile and stress corrosion behavior of the aged weld metal have been attributed to the two competitive processes of matrix softening and hardening. Yield strength (YS) was found to depend predominantly on matrix softening only, while sig-nificant changes in the ultimate tensile strength (UTS) and the work-hardening exponent, n, occurred due to matrix hardening. Ductility and stress corrosion properties were considerably affected by both factors. Fractographic observations on the weld metal tested for stress-corrosion cracking (SCC) indicated a combination of transgranular cracking of the austenite and interface cracking.

In-vitro biodegradation and corrosion-assisted cracking of a coated magnesium alloy in modified-simulated body fluid.

PubMed

Jafari, Sajjad; Singh Raman, R K

2017-09-01

A calcium phosphate coating was directly synthesized on AZ91D magnesium (Mg) alloy. Resistance of this coating to corrosion in a modified-simulated body fluid (m-SBF) was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Mechanical properties of the bare and coated alloy were investigated using slow strain rate tensile (SSRT) and fatigue testing in air and m-SBF. Very little is reported in the literature on human-body-fluid-assisted cracking of Mg alloys, viz., resistance to corrosion fatigue (CF) and stress corrosion cracking (SCC). This study has a particular emphasis on the effect of bio-compatible coatings on mechanical and electrochemical degradations of Mg alloys for their applications as implants. The results suggest the coating to improve the general as well as pitting corrosion resistance of the alloy. The coating also provides visible improvement in resistance to SCC, but little improvement in CF resistance. This is explained on the basis of pitting behaviour in the presence and absence of the coating. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of chloride-induced corrosion in pre-cracked RC beams under sustained loading: Effect of load-induced cracks, concrete cover, and exposure conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Linwen; Université de Sherbrooke, Quebec; François, Raoul, E-mail: raoul.francois@insa-toulouse.fr

2015-01-15

This paper deals with corrosion initiation and propagation in pre-cracked reinforced concrete beams under sustained loading during exposure to a chloride environment. Specimen beams that were cast in 2010 were compared to specimens cast in 1984. The only differences between the two sets of beams were the casting direction in relation to tensile reinforcement and the exposure conditions in the salt-fog chamber. The cracking maps, corrosion maps, chloride profiles, and cross-sectional loss of one group of two beams cast in 2010 were studied and their calculated corrosion rates were compared to that of beams cast in 1984 in order tomore » investigate the factors influencing the natural corrosion process. Experimental results show that, after rapid initiation of corrosion at the crack tip, the corrosion process practically halted and the time elapsing before corrosion resumed depended on the exposure conditions and cover depth.« less

Corrosion Development of Carbon Steel Grids and Shear Connectors in Cracked Composite Beams Exposed to Wet–Dry Cycles in Chloride Environment

PubMed Central

Xue, Wen; Chen, Ju; Jiang, Ao-yu

2018-01-01

The corrosion development of the reinforcement and shear stud connectors in the cracked steel–concrete composite beams under the salt-fog wet–dry cycles is presented in this investigation. Seven identical composite beams with load-induced concrete cracks were exposed to an aggressive chloride environment. The reinforcement and shear connectors were retrieved after specimens underwent a specified number of wet–dry cycles to obtain the corrosion pattern and the cross-section loss at different exposure times and their evolutions. The crack map, the corrosion pattern and the cross-section loss were measured and presented. Based on the experimental results, the influence of crack characteristics, including crack widths, orientations and positions on the corrosion rate and distribution, were accessed. Moreover, the effects of the connecting weldments on the corrosion initiations and patterns were analyzed. It was shown that the corrosion rate would increase with the number of wet–dry cycles. The characteristics of load-induced cracks could have different influences on the steel grids and shear stud connectors. The corrosion tended to initiate from the connecting weldments, due to the potential difference with the parent steel and the aggressive exposure environment, leading to a preferential weldment attack. PMID:29565836

Effects of Nitrogen and Tensile Direction on Stress Corrosion Cracking Susceptibility of Ni-Free FeCrMnC-Based Duplex Stainless Steels

PubMed Central

Ha, Heon-Young; Lee, Chang-Hoon; Lee, Tae-Ho; Kim, Sangshik

2017-01-01

Stress corrosion cracking (SCC) behavior of Ni-free duplex stainless steels containing N and C (Febalance-19Cr-8Mn-0.25C-(0.03, 0.21)N, in wt %) was investigated by using a slow strain rate test (SSRT) in air and aqueous NaCl solution with different tensile directions, including parallel (longitudinal) and perpendicular (transverse) to the rolling direction. It was found that alloying N was effective in increasing the resistance to SCC, while it was higher along the longitudinal direction than the transverse direction. The SCC susceptibility of the two alloys was assessed based on the electrochemical resistance to pitting corrosion, the corrosion morphology, and the fractographic analysis. PMID:28772651

External stress-corrosion cracking of a 1.22-m-diameter type 316 stainless steel air valve

NASA Technical Reports Server (NTRS)

Moore, Thomas J.; Telesman, Jack; Moore, Allan S.; Johnson, Dereck F.; Kuivinen, David E.

1993-01-01

An investigation was conducted to determine the cause of the failure of a massive AISI Type 316 stainless steel valve which controlled combustion air to a jet engine test facility. Several through-the-wall cracks were present near welded joints in the valve skirt. The valve had been in outdoor service for 18 years. Samples were taken in the cracked regions for metallographic and chemical analyses. Insulating material and sources of water mist in the vicinity of the failed valve were analyzed for chlorides. A scanning electron microscope was used to determine whether foreign elements were present in a crack. On the basis of the information generated, the failure was characterized as external stress-corrosion cracking. The cracking resulted from a combination of residual tensile stress from welding and the presence of aqueous chlorides. Recommended countermeasures are included.

Uniaxial low cycle fatigue behavior for pre-corroded 16MND5 bainitic steel in simulated pressurized water reactor environment

NASA Astrophysics Data System (ADS)

Chen, Xu; Ren, Bin; Yu, Dunji; Xu, Bin; Zhang, Zhe; Chen, Gang

2018-06-01

The effects of uniaxial tension properties and low cycle fatigue behavior of 16MND5 bainitic steel cylinder pre-corroded in simulated pressurized water reactor (PWR) were investigated by fatigue at room temperature in air and immersion test system, scanning electron microscopy (SEM), energy disperse spectroscopy (EDS). The experimental results indicated that the corrosion fatigue lives of 16MND5 specimen were significantly affected by the strain amplitude and simulated PWR environments. The compositions of corrosion products were complexly formed in simulated PWR environments. The porous corrosion surface of pre-corroded materials tended to generate pits as a result of promoting contact area to the fresh metal, which promoted crack initiation. For original materials, the fatigue cracks initiated at inclusions imbedded in the micro-cracks. Moreover, the simulated PWR environments degraded the mechanical properties and low cycle fatigue behavior of 16MND5 specimens remarkably. Pre-corrosion of 16MND5 specimen mainly affected the plastic term of the Coffin-Manson equation.

Stress Corrosion Cracking Behavior of X80 Pipeline Steel in Acid Soil Environment with SRB

NASA Astrophysics Data System (ADS)

Wang, Dan; Xie, Fei; Wu, Ming; Liu, Guangxin; Zong, Yue; Li, Xue

2017-06-01

Self-designed experimental device was adopted to ensure the normal growth of sulphate-reducing bacteria (SRB) in sterile simulated Yingtan soil solution. Stress corrosion cracking (SCC) behavior of X80 pipeline steel in simulated acid soil environment was investigated by electrochemical impedance spectroscopy, slow strain rate test, and scanning electron microscope. Results show that the presence of SRB could promote stress corrosion cracking susceptibility. In a growth cycle, polarization resistance first presents a decrease and subsequently an increase, which is inversely proportional to the quantities of SRB. At 8 days of growth, SRB reach their largest quantity of 1.42 × 103 cells/g. The corrosion behavior is most serious at this time point, and the SCC mechanism is hydrogen embrittlement. In other SRB growth stages, the SCC mechanism of X80 steel is anodic dissolution. With the increasing SRB quantities, X80 steel is largely prone to SCC behavior, and the effect of hydrogen is considerably obvious.

Synthetic sea water - An improved stress corrosion test medium for aluminum alloys

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1973-01-01

A major problem in evaluating the stress corrosion cracking resistance of aluminum alloys by alternate immersion in 3.5 percent salt (NaCl) water is excessive pitting corrosion. Several methods were examined to eliminate this problem and to find an improved accelerated test medium. These included the addition of chromate inhibitors, surface treatment of specimens, and immersion in synthetic sea water. The results indicate that alternate immersion in synthetic sea water is a very promising stress corrosion test medium. Neither chromate inhibitors nor surface treatment (anodize and alodine) of the aluminum specimens improved the performance of alternate immersion in 3.5 percent salt water sufficiently to be classified as an effective stress corrosion test method.

75 FR 70812 - Airworthiness Directives; Sikorsky Aircraft Corporation (Sikorsky) Model S-92A Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-19

... corrosion. If you do not find a crack, the AD requires applying a corrosion preventive compound. If you find a crack, the AD requires replacing the MGB before further flight. If you find corrosion, bubbled... include another MGB assembly and MGB housing that is prone to the same cracks and corrosion as the MGB...

Assessment of Stress Corrosion Cracking Resistance of Activated Tungsten Inert Gas-Welded Duplex Stainless Steel Joints

NASA Astrophysics Data System (ADS)

Alwin, B.; Lakshminarayanan, A. K.; Vasudevan, M.; Vasantharaja, P.

2017-12-01

The stress corrosion cracking behavior of duplex stainless steel (DSS) weld joint largely depends on the ferrite-austenite phase microstructure balance. This phase balance is decided by the welding process used, heat input, welding conditions and the weld metal chemistry. In this investigation, the influence of activated tungsten inert gas (ATIG) and tungsten inert gas (TIG) welding processes on the stress corrosion cracking (SCC) resistance of DSS joints was evaluated and compared. Boiling magnesium chloride (45 wt.%) environment maintained at 155 °C was used. The microstructure and ferrite content of different weld zones are correlated with the outcome of sustained load, SCC test. Irrespective of the welding processes used, SCC resistance of weld joints was inferior to that of the base metal. However, ATIG weld joint exhibited superior resistance to SCC than the TIG weld joint. The crack initiation and final failure were in the weld metal for the ATIG weld joint; they were in the heat-affected zone for the TIG weld joint.

Stress Corrosion Cracking of an Austenitic Stainless Steel in Nitrite-Containing Chloride Solutions

PubMed Central

Singh Raman, R. K.; Siew, Wai Hoong

2014-01-01

This article describes the susceptibility of 316L stainless steel to stress corrosion cracking (SCC) in a nitrite-containing chloride solution. Slow strain rate testing (SSRT) in 30 wt. % MgCl2 solution established SCC susceptibility, as evidenced by post-SSRT fractography. Addition of nitrite to the chloride solution, which is reported to have inhibitive influence on corrosion of stainless steels, was found to increase SCC susceptibility. The susceptibility was also found to increase with nitrite concentration. This behaviour is explained on the basis of the passivation and pitting characteristics of 316L steel in chloride solution. PMID:28788276

Degradation and mechanism of the mechanics and durability of reinforced concrete slab in a marine environment

NASA Astrophysics Data System (ADS)

Wu, Sheng-xing; Liu, Guan-guo; Bian, Han-bing; Lv, Wei-bo; Jiang, Jian-hua

2016-04-01

An experimental research was conducted to determine the corrosion and bearing capacity of a reinforced concrete (RC) slab at different ages in a marine environment. Results show that the development of corrosion-induced cracks on a slab in a marine environment can be divided into three stages according to crack morphology at the bottom of the slab. In the first stage, cracks appear. In the second stage, cracks develop from the edges to the middle of the slab. In the third stage, longitudinal and transverse corrosion-induced cracks coexist. The corrosion ratio of reinforcements nonlinearly increases with the age, and the relationship between the corrosion ratio of the reinforcements and the corrosion-induced crack width of the concrete is established. The flexural capacity of the corroded RC slab nonlinearly decreases with the age, and the model for the bearing capacity factor of the corroded RC slab is established. The mid-span deflection of the corroded RC slab that corresponds to the yield of the reinforcements linearly increases with the increase in corrosion ratio. Finally, the mechanisms of corrosion morphology and the degradation of the mechanical properties of an RC slab in a marine environment are discussed on the basis of the basic theories of steel corrosion in concrete and concrete structure design.

77 FR 60285 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-03

... the MLG for chicken- wire cracks, corrosion, and chrome plate distress; repetitive magnetic particle... center axles of the MLG for chicken-wire cracks, corrosion, and chrome plate distress; repetitive... the MLG for chicken- wire cracks, corrosion, and chrome plate distress; do a magnetic particle...

The role of hydrogen in hot-salt stress corrosion cracking of titanium-aluminum alloys

NASA Technical Reports Server (NTRS)

Ondrejcin, R. S.

1971-01-01

Additional support is presented for the previously proposed role of hydrogen as an embrittling agent in hot-salt stress corrosion cracking of titanium-aluminum alloys. The main source of hydrogen formed during the reactions of titanium alloys with hot salt was identified as water associated with the salt. Hydrogen is produced by the reaction of an intermediate (hydrogen halide) with the alloy rather than from metal-water reactions. The fracture mode of precracked tensile specimens was ductile when the specimens were tested in air, and brittle when tests were made in high-pressure hydrogen. Stressed titanium-aluminum alloys also were cracked by bombardment with hydrogen ions produced in a proton accelerator. The approximate concentrations of the hydrogen ions in the alloys were calculated.

Experimental Evaluation of Fatigue Crack Initiation from Corroded Hemispherical Notches in Aerospace Structural Materials

NASA Technical Reports Server (NTRS)

Garcia, Daniel B.; Forman, Royce; Shindo, David

2010-01-01

A test program was developed and executed to evaluate the influence of corroded hemispherical notches on the fatigue crack initiation and propagation in aluminum 7075-T7351, 4340 steel, and D6AC steel. Surface enhancements such as shot peening and laser shock peening were also incorporated as part of the test effort with the intent of improving fatigue performance. In addition to the testing, fracture mechanics and endurance limit based analysis methods were evaluated to characterize the results with the objective of challenging typical assumptions used in modeling fatigue cracks from corrosion pits. The results specifically demonstrate that the aluminum and steel alloys behave differently with respect to fatigue crack initiation from hemispherical corrosion pits. The aluminum test results were bounded by the fracture mechanics and endurance limit models while exhibiting a general insensitivity to the residual stress field generated by shot peening. The steel specimens were better characterized by the endurance limit fatigue properties and did exhibit sensitivities to residual stresses from the shot peening and laser shock peening

Corrosion and Corrosion Control in Light Water Reactors

NASA Astrophysics Data System (ADS)

Gordon, Barry M.

2013-08-01

Serious corrosion problems have plagued the light water reactor (LWR) industry for decades. The complex corrosion mechanisms involved and the development of practical engineering solutions for their mitigation will be discussed in this article. After a brief overview of the basic designs of the boiling water reactor (BWR) and pressurized water reactor (PWR), emphasis will be placed on the general corrosion of LWR containments, flow-accelerated corrosion of carbon steel components, intergranular stress corrosion cracking (IGSCC) in BWRs, primary water stress corrosion cracking (PWSCC) in PWRs, and irradiation-assisted stress corrosion cracking (IASCC) in both systems. Finally, the corrosion future of both plants will be discussed as plants extend their period of operation for an additional 20 to 40 years.

Stress Corrosion Testing

NASA Technical Reports Server (NTRS)

1985-01-01

Advanced testing of structural materials was developed by Lewis Research Center and Langley Research Center working with the American Society for Testing and Materials (ASTM). Under contract, Aluminum Company of America (Alcoa) conducted a study for evaluating stress corrosion cracking, and recommended the "breaking load" method which determines fracture strengths as well as measuring environmental degradation. Alcoa and Langley plan to submit the procedure to ASTM as a new testing method.

Stress-corrosion cracking in metals

NASA Technical Reports Server (NTRS)

1971-01-01

Criteria and recommended practices for preventing stress-corrosion cracking from impairing the structural integrity and flightworthiness of space vehicles are presented. The important variables affecting stress-corrosion cracking are considered to be the environment, including time and temperature; metal composition, and structure; and sustained tensile stress. For designing spacecraft structures that are free of stress-corrosion cracking for the service life of the vehicle the following rules apply: (1) identification and control of the environments to which the structure will be exposed during construction, storage, transportation, and use; (2) selection of alloy compositions and tempers which are resistant to stress-corrosion cracking in the identified environment; (3) control of fabrication and other processes which may introduce residual tensile stresses or damage the material; (4) limitation of the combined residual and applied tensile stresses to below the threshold stress level for the onset of cracking throughout the service life of the vehicle; and (5) establishment of a thorough inspection program.

Fracture Behavior of Ceramics Under Displacement Controlled Loading

NASA Technical Reports Server (NTRS)

Calomino, Anthony; Brewer, David; Ghosn, Louis

1994-01-01

A Mode I fracture specimen and loading method has been developed which permits the observation of stable crack extension in monolithic and in situ toughened ceramics. The developed technique was used to conduct room temperature tests on commercial grade alumina (Coors' AD-995) and silicon nitride (Norton NC-132). The results of these tests are reported. Crack growth for the alumina remained subcritical throughout testing revealing possible effects of environmental stress corrosion. The crack growth resistance curve for the alumina is presented. The silicon nitride tests displayed a series of stable (slow) crack growth segments interrupted by dynamic (rapid) crack extension. Crack initiation and arrest stress intensity factors, K(sub Ic) and K(sub Ia), for silicon nitride are reported. The evolution of the specimen design through testing is briefly discussed.

Corrosion pitting and environmentally assisted small crack growth

PubMed Central

Turnbull, Alan

2014-01-01

In many applications, corrosion pits act as precursors to cracking, but qualitative and quantitative prediction of damage evolution has been hampered by lack of insights into the process by which a crack develops from a pit. An overview is given of recent breakthroughs in characterization and understanding of the pit-to-crack transition using advanced three-dimensional imaging techniques such as X-ray computed tomography and focused ion beam machining with scanning electron microscopy. These techniques provided novel insights with respect to the location of crack development from a pit, supported by finite-element analysis. This inspired a new concept for the role of pitting in stress corrosion cracking based on the growing pit inducing local dynamic plastic strain, a critical factor in the development of stress corrosion cracks. Challenges in quantifying the subsequent growth rate of the emerging small cracks are then outlined with the potential drop technique being the most viable. A comparison is made with the growth rate for short cracks (through-thickness crack in fracture mechanics specimen) and long cracks and an electrochemical crack size effect invoked to rationalize the data. PMID:25197249

78 FR 72598 - Airworthiness Directives; British Aerospace Regional Aircraft Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-03

... product. The MCAI describes the unsafe condition as stress corrosion cracking of the main landing gear.... The subsequent investigation revealed stress corrosion cracking of the MLG yoke pintle housing as a..., consequently, stress corrosion cracking. This condition, if not corrected, could lead to structural failure of...

49 CFR 192.929 - What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)?

Code of Federal Regulations, 2011 CFR

2011-10-01

... Assessment for Stress Corrosion Cracking (SCCDA)? 192.929 Section 192.929 Transportation Other Regulations...: MINIMUM FEDERAL SAFETY STANDARDS Gas Transmission Pipeline Integrity Management § 192.929 What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)? (a) Definition. Stress...

49 CFR 192.929 - What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)?

Code of Federal Regulations, 2012 CFR

2012-10-01

... Assessment for Stress Corrosion Cracking (SCCDA)? 192.929 Section 192.929 Transportation Other Regulations...: MINIMUM FEDERAL SAFETY STANDARDS Gas Transmission Pipeline Integrity Management § 192.929 What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)? (a) Definition. Stress...

49 CFR 192.929 - What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)?

Code of Federal Regulations, 2014 CFR

2014-10-01

... Assessment for Stress Corrosion Cracking (SCCDA)? 192.929 Section 192.929 Transportation Other Regulations...: MINIMUM FEDERAL SAFETY STANDARDS Gas Transmission Pipeline Integrity Management § 192.929 What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)? (a) Definition. Stress...

49 CFR 192.929 - What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)?

Code of Federal Regulations, 2013 CFR

2013-10-01

... Assessment for Stress Corrosion Cracking (SCCDA)? 192.929 Section 192.929 Transportation Other Regulations...: MINIMUM FEDERAL SAFETY STANDARDS Gas Transmission Pipeline Integrity Management § 192.929 What are the requirements for using Direct Assessment for Stress Corrosion Cracking (SCCDA)? (a) Definition. Stress...

Replacement of corrosion protection chromate primers and paints used in cryogenic applications on the Space Shuttle with wire arc sprayed aluminum coatings

NASA Technical Reports Server (NTRS)

Daniel, R. L.; Sanders, H. L.; Zimmerman, F. R.

1995-01-01

With the advent of new environmental laws restricting volatile organic compounds and hexavalent chrome emissions, 'environmentally safe' thermal spray coatings are being developed to replace the traditional corrosion protection chromate primers. A wire arc sprayed aluminum coating is being developed for corrosion protection of low pressure liquid hydrogen carrying ducts on the Space Shuttle Main Engine. Currently, this hardware utilizes a chromate primer to provide protection against corrosion pitting and stress corrosion cracking induced by the cryogenic operating environment. The wire are sprayed aluminum coating has been found to have good potential to provide corrosion protection for flight hardware in cryogenic applications. The coating development, adhesion test, corrosion test and cryogenic flexibility test results will be presented.

Effects of crack tip plastic zone on corrosion fatigue cracking of alloy 690(TT) in pressurized water reactor environments

NASA Astrophysics Data System (ADS)

Xiao, J.; Qiu, S. Y.; Chen, Y.; Fu, Z. H.; Lin, Z. X.; Xu, Q.

2015-01-01

Alloy 690(TT) is widely used for steam generator tubes in pressurized water reactor (PWR), where it is susceptible to corrosion fatigue. In this study, the corrosion fatigue behavior of Alloy 690(TT) in simulated PWR environments was investigated. The microstructure of the plastic zone near the crack tip was investigated and labyrinth structures were observed. The relationship between the crack tip plastic zone and fatigue crack growth rates and the environment factor Fen was illuminated.

Corrosion Fatigue Characteristics of 12Cr Alloy Steel in Na2SO4 Solution

NASA Astrophysics Data System (ADS)

Bae, D. H.; Cho, S. Y.

In order to estimate reliability of 12Cr alloy steel using as the turbine blade material of the steam power plant, its corrosion fatigue characteristics in Na2SO4 solution considering its percentage and temperature that were determined from the polarization test results were investigated, and compared with the results in air. The corrosion characteristic of 12Cr alloy steel was remarkably susceptible in 12.7wt.% (IM) Na2SO4 solution, and its susceptibility increased with the solution temperature increase. The corrosion fatigue characteristics in 12.7wt.% Na2SO4 solution were similar to that of in air at 25°C. The crack growth rate was however increased with the temperature of solution increase. The reasons showing such results are due to the difference of the crack growth mechanism according to the electro-chemical activity of the corrosion factors.

Chloride-induced corrosion of steel in cracked concrete – Part I: Experimental studies under accelerated and natural marine environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Otieno, M., E-mail: Mike.Otieno@wits.ac.za; Beushausen, H.; Alexander, M.

Parallel corrosion experiments were carried out for 2¼ years by exposing one half of 210 beam specimens (120 × 130 × 375 mm long) to accelerated laboratory corrosion (cyclic wetting and drying) while the other half underwent natural corrosion in a marine tidal zone. Experimental variables were crack width w{sub cr} (0, incipient crack, 0.4, 0.7 mm), cover c (20, 40 mm), binder type (PC, PC/GGBS, PC/FA) and w/b ratio (0.40, 0.55). Results show that corrosion rate (i{sub corr}) was affected by the experimental variables in the following manner: i{sub corr} increased with increase in crack width, and decreased withmore » increase in concrete quality and cover depth. The results also show that the corrosion performance of concretes in the field under natural corrosion cannot be inferred from its performance in the laboratory under accelerated corrosion. Other factors such as corrosion process should be taken into account.« less

In-Pile Tests for IASCC Growth Behavior of Irradiated 316L Stainless Steel under Simulated BWR Condition in JMTR

NASA Astrophysics Data System (ADS)

Chimi, Yasuhiro; Kasahara, Shigeki; Ise, Hideo; Kawaguchi, Yoshihiko; Nakano, Junichi; Nishiyama, Yutaka

The Japan Atomic Energy Agency (JAEA) has an in-pile irradiation test plan to evaluate in-situ effects of neutron/γ-ray irradiation on stress corrosion crack (SCC) growth of irradiated stainless steels using the Japan Materials Testing Reactor (JMTR). SCC growth rate and its dependence on electrochemical corrosion potential (ECP) are different between in-pile test and post irradiation examination (PIE). These differences are not fully understood because of a lack of in-pile data. This paper presents a systematic review on SCC growth data of irradiated stainless steels, an in-pile test plan for crack growth of irradiated SUS316L stainless steel under simulated BWR conditions in the JMTR, and the development of the in-pile test techniques.

Recent progress to understand stress corrosion cracking in sodium borosilicate glasses: linking the chemical composition to structural, physical and fracture properties

NASA Astrophysics Data System (ADS)

Rountree, Cindy L.

2017-08-01

This topical review is dedicated to understanding stress corrosion cracking in oxide glasses and specifically the SiO_2{\\text-B_2O_3{\\text-}Na_2O} (SBN) ternary glass systems. Many review papers already exist on the topic of stress corrosion cracking in complex oxide glasses or overly simplified glasses (pure silica). These papers look at how systematically controlling environmental factors (pH, temperature...) alter stress corrosion cracking, while maintaining the same type of glass sample. Many questions still exist, including: What sets the environmental limit? What sets the velocity versus stress intensity factor in the slow stress corrosion regime (Region I)? Can researchers optimize these two effects to enhance a glass’ resistance to failure? To help answer these questions, this review takes a different approach. It looks at how systemically controlling the glass’ chemical composition alters the structure and physical properties. These changes are then compared and contrasted to the fracture toughness and the stress corrosion cracking properties. By taking this holistic approach, researchers can begin to understand the controlling factors in stress corrosion cracking and how to optimize glasses via the initial chemical composition.

Improved stress corrosion cracking resistance of a novel biodegradable EW62 magnesium alloy by rapid solidification, in simulated electrolytes.

PubMed

Hakimi, O; Aghion, E; Goldman, J

2015-06-01

The high corrosion rate of magnesium (Mg) and Mg-alloys precludes their widespread acceptance as implantable biomaterials. Here, we investigated the potential for rapid solidification (RS) to increase the stress corrosion cracking (SCC) resistance of a novel Mg alloy, Mg-6%Nd-2%Y-0.5%Zr (EW62), in comparison to its conventionally cast (CC) counterpart. RS ribbons were extrusion consolidated in order to generate bioimplant-relevant geometries for testing and practical use. Microstructural characteristics were examined by SEM. Corrosion rates were calculated based upon hydrogen evolution during immersion testing. The surface layer of the tested alloys was analyzed by X-ray photoelectron spectroscopy (XPS). Stress corrosion resistance was assessed by slow strain rate testing and fractography. The results indicate that the corrosion resistance of the RS alloy is significantly improved relative to the CC alloy due to a supersaturated Nd enrichment that increases the Nd2O3 content in the external oxide layer, as well as a more homogeneous structure and reduced grain size. These improvements contributed to the reduced formation of hydrogen gas and hydrogen embrittlement, which reduced the SCC sensitivity relative to the CC alloy. Therefore, EW62 in the form of a rapidly solidified extruded structure may serve as a biodegradable implant for biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of Soft Drinks with Low pH on Different Ni-Ti Orthodontic Archwire Surface Patterns

NASA Astrophysics Data System (ADS)

Abalos, C.; Paul, A.; Mendoza, A.; Solano, E.; Palazon, C.; Gil, F. J.

2013-03-01

The aim of this study was to determine the influence of soft drinks on the surface of Ni-Ti archwires and their corrosion behavior. Archwires with different patterns (smooth, scratch, dimple, and crack) were selected and characterized by scanning electron microscopy and laser confocal microscopy. Immersion tests were performed in artificial saliva (pH 6.7) with a soft drink with a pH of 2.5 for 28 days. The results showed an increase in the surface defects and/or roughness of the dimple, crack and scratch patterns with the immersion times, and a decrease in corrosion resistance. A relationship between the surface pattern and the extent of the corrosion in Ni-Ti archwires with soft drinks at low pH has been demonstrated. Pattern should be taken into account in future studies, and manufacturing processes that produce surface defects (especially cracks) should be avoided.

On ripple-load, stress-corrosion, and sustained-load cracking behavior in a high strength beta titanium alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pao, P.S.; Meyn, D.A.; Bayles, R.A.

1997-06-01

Both overaged and peakaged TIMETAL 21S beta titanium alloys exhibit significant ripple-load cracking susceptibility in salt water and in ambient air environments. At R = 0.90, the ripple-load cracking thresholds of the overaged alloy are 67% and 72% lower than the stress-corrosion cracking and sustained-load cracking thresholds. For the peakaged alloy, the reductions are 55% and 61%. The stress-corrosion cracking threshold in salt water and the sustained-load cracking threshold in air of peakaged TIMETAL 21S are significantly lower while the ripple-load cracking threshold is slightly lower than those of the overaged alloy. The stress-corrosion cracking, sustained-load cracking, and ripple-load crackingmore » resistance of peakaged TIMETAL 21S are significantly inferior to those of both beta-annealed Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn. The ripple-load cracking resistance of overaged TIMETAL 21S, though better than Ti-15V-3Cr-3Al-3Sn, is still inferior than that of beta-annealed Ti-6Al-4V.« less

Corrosion and stress corrosion cracking in supercritical water

NASA Astrophysics Data System (ADS)

Was, G. S.; Ampornrat, P.; Gupta, G.; Teysseyre, S.; West, E. A.; Allen, T. R.; Sridharan, K.; Tan, L.; Chen, Y.; Ren, X.; Pister, C.

2007-09-01

Supercritical water (SCW) has attracted increasing attention since SCW boiler power plants were implemented to increase the efficiency of fossil-based power plants. The SCW reactor (SCWR) design has been selected as one of the Generation IV reactor concepts because of its higher thermal efficiency and plant simplification as compared to current light water reactors (LWRs). Reactor operating conditions call for a core coolant temperature between 280 °C and 620 °C at a pressure of 25 MPa and maximum expected neutron damage levels to any replaceable or permanent core component of 15 dpa (thermal reactor design) and 100 dpa (fast reactor design). Irradiation-induced changes in microstructure (swelling, radiation-induced segregation (RIS), hardening, phase stability) and mechanical properties (strength, thermal and irradiation-induced creep, fatigue) are also major concerns. Throughout the core, corrosion, stress corrosion cracking, and the effect of irradiation on these degradation modes are critical issues. This paper reviews the current understanding of the response of candidate materials for SCWR systems, focusing on the corrosion and stress corrosion cracking response, and highlights the design trade-offs associated with certain alloy systems. Ferritic-martensitic steels generally have the best resistance to stress corrosion cracking, but suffer from the worst oxidation. Austenitic stainless steels and Ni-base alloys have better oxidation resistance but are more susceptible to stress corrosion cracking. The promise of grain boundary engineering and surface modification in addressing corrosion and stress corrosion cracking performance is discussed.

Influences of Cr/Ni equivalent ratios of filler wires on pitting corrosion and ductility-dip cracking of AISI 316L weld metals

NASA Astrophysics Data System (ADS)

Kim, Y. H.; Kim, D. G.; Sung, J. H.; Kim, I. S.; Ko, D. E.; Kang, N. H.; Hong, H. U.; Park, J. H.; Lee, H. W.

2011-02-01

To study the pitting corrosion of AISI 316L weld metals according to the chromium/nickel equivalent ratio (Creq/Nieq ratio), three filler wires were newly designed for the flux-cored arc welding process. The weld metal with delta-ferrite at less than 3 vol.%, was observed for ductility-dip cracking (DDC) in the reheated region after multi-pass welding. The tensile strength and yield strength increased with increasing Creq/Nieq ratio. The result of anodic polarization tests in a 0.1 M NaCl solution at the room temperature (25) for 45 min, revealed that the base metal and weld metals have a similar corrosion potential of -0.34 VSCE. The weld metal with the highest content of Cr had the highest pitting potential (0.39 VSCE) and the passivation range (0.64 VSCE) was higher than the base metal (0.21 VSCE and 0.46 VSCE, respectively). Adding 0.001 M Na2S to the 0.1M NaCl solution, the corrosion occurred more severely by H2S. The corrosion potentials of the base metal and three weld metals decreased to -1.0 VSCE. DDC caused the decrease of the pitting potential by inducing a locally intense corrosion attack around the crack openings.

78 FR 4053 - Airworthiness Directives; PILATUS Aircraft Ltd. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-18

... fittings caused by stress corrosion. We are issuing this AD to require actions to address the unsafe... prompted due to the discovery of cracks in the engine mount fittings. The cracks are caused by stress corrosion. It is possible for stress corrosion cracks to occur on engine mount fittings initially made of...

78 FR 2195 - Airworthiness Directives; Rolls-Royce Deutschland Ltd & Co KG Turbofan Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-10

... of silver chloride-induced stress corrosion cracking of the HP compressor stages 1 to 6 rotor disc...: Silver chloride-induced stress corrosion cracking was identified during overhaul of a BR700-715 engine... a report of silver chloride-induced stress corrosion cracking of the high-pressure (HP) compressor...

76 FR 69168 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-08

... examination of the cracked ribs confirmed that the cracks were the result of pitting corrosion in the forward lug hole. Also on both aeroplanes, medium to heavy corrosion was found in the forward lugs on the... ribs confirmed that the cracks were the result of pitting corrosion in the forward lug hole. Also on...

77 FR 28328 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-14

... loose or missing fastener, a crack, damage, or corrosion and adding an internal doubler to the aft shear... proposed actions are intended to detect a loose or missing fastener, a crack, damage, or corrosion on the T... inspection of the T/R pylon ``components and structure for obvious damage, cracks, corrosion, and security...

An Industrial Perspective on Environmentally Assisted Cracking of Some Commercially Used Carbon Steels and Corrosion-Resistant Alloys

NASA Astrophysics Data System (ADS)

Ashida, Yugo; Daigo, Yuzo; Sugahara, Katsuo

2017-08-01

Commercial metals and alloys like carbon steels, stainless steels, and nickel-based super alloys frequently encounter the problem of environmentally assisted cracking (EAC) and resulting failure in engineering components. This article aims to provide a perspective on three critical industrial applications having EAC issues: (1) corrosion and cracking of carbon steels in automotive applications, (2) EAC of iron- and nickel-based alloys in salt production and processing, and (3) EAC of iron- and nickel-based alloys in supercritical water. The review focuses on current industrial-level understanding with respect to corrosion fatigue, hydrogen-assisted cracking, or stress corrosion cracking, as well as the dominant factors affecting crack initiation and propagation. Furthermore, some ongoing industrial studies and directions of future research are also discussed.

Disbond Detection in Bonded Aluminum Joints Using Lamb Wave Amplitude and Time-of-Flight

NASA Technical Reports Server (NTRS)

Sun, Keun J.; Johnston, Patrick H.

1992-01-01

In recent years, there was a need of developing efficient nondestructive integrity assessment techniques for large area laminate structures, such as detections of disbond, crack, and corrosion in fuselage of an aircraft. Together with the improving tomography and computer technologies, progress has been made in many fields in NDE towards a faster inspection. Ultrasonically, Lamb wave is considered to be a candidate for large area inspections based on its capability of propagating a relatively long distance in thin plates and its media-thickness-dependent propagation properties. Moreover, the occurence of disbonds, corrosion, and even cracks often results in reduction of effective thickness of a laminate. The idea is to assess the condition of a structure by sensing the response of propagating Lamb waves to these flaws over long path length. A series of tests in the sequence of disbond, corrosion, and crack have been done on various types of specimen to investigate the feasibility of this approach. This paper will present some of the test results for disbond detection on aluminum lap splice joints.

Stress Corrosion Cracking of High Strength Steels

DTIC Science & Technology

1995-06-01

R. Brown, J. H. Graves, E. U. Lee, C. E. Neu and J. Kozol, " Corrosion Behavior of High Strength Steels for Aerospace Applications," Proceedings of...h fit Stress Corrosion Cracking of High Strength Steels Eun U. Lee, Henry Sanders and Bhaskar Sarkar Naval Air Warfare Center Aircraft Division...Patuxent River, Maryland 20670 ABSTRACT The stress corrosion cracking (SCC) was investigated for AerMet 100 and 300M steels in four aqueous NaCl

Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading

NASA Technical Reports Server (NTRS)

Forman, Royce G.; Zanganehgheshlaghi, Mohannad

2014-01-01

The research results described in this paper presents a new understanding of the behavior of fatigue crack growth in the threshold region. It is believed by some crack growth experts that the ASTM load shedding test method does not produce true or valid threshold properties. The concern involves the observed fanning of threshold region da/dN data plots for some materials in which the low R-ratio data fans out or away from the high R-ratio data. This data fanning or elevation of threshold values is obviously caused by an increase in crack closure in the low R-ratio tested specimens. This increase in crack closure is assumed by some investigators to be caused by a plastic wake on the crack surfaces that was created during the load shedding test phase. This study shows that the increase in crack closure is the result of an extensive occurrence of crack bifurcation behavior in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the particular fanning behavior in aluminum alloys is a function of intrinsic dislocation property of the materials and that the fanned data represents valid material properties. However, for corrosion sensitive steel alloys used in this study the fanning was caused by a build-up of iron oxide at the crack tip from fretting corrosion.

Stress Corrosion Cracking and Fatigue Crack Growth Studies Pertinent to Spacecraft and Booster Pressure Vessels

NASA Technical Reports Server (NTRS)

Hall, L. R.; Finger, R. W.

1972-01-01

This experimental program was divided into two parts. The first part evaluated stress corrosion cracking in 2219-T87 aluminum and 5Al-2.5Sn (ELI) titanium alloy plate and weld metal. Both uniform height double cantilever beam and surface flawed specimens were tested in environments normally encountered during the fabrication and operation of pressure vessels in spacecraft and booster systems. The second part studied compatibility of material-environment combinations suitable for high energy upper stage propulsion systems. Surface flawed specimens having thicknesses representative of minimum gage fuel and oxidizer tanks were tested. Titanium alloys 5Al-2.5Sn (ELI), 6Al-4V annealed, and 6Al-4V STA were tested in both liquid and gaseous methane. Aluminum alloy 2219 in the T87 and T6E46 condition was tested in fluorine, a fluorine-oxygen mixture, and methane. Results were evaluated using modified linear elastic fracture mechanics parameters.

75 FR 5684 - Airworthiness Directives; Sikorsky Aircraft Corporation Model S-92A Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-04

... pad and rib for a crack and corrosion. If you do not find a crack, the AD requires applying a corrosion preventive compound. If you find a crack, the AD requires replacing the MGB before further flight. If you find corrosion, bubbled paint, or paint discoloration, the AD also requires you to repair the...

77 FR 68061 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-15

...) pylon for a loose or missing fastener, a crack, damage, or corrosion and adding an internal doubler to... actions are intended to detect a loose or missing fastener, a crack, damage, or corrosion on the T/R pylon..., a crack, damage, or corrosion, and repairing or replacing the T/R pylon if any of these conditions...

Alloy 690 qualification: Corrosion under prototypic heat flux and temperature conditions. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baum, A.J.

1995-05-01

The objective of this program was to perform qualification tests of industrial heats of thermally treated alloy 690 steam generator tubing under heat transfer conditions. Primary emphasis was focused on testing of alternate tube to tubesheet expansion processes. In addition, a background report was written to document the evolution of the alloy 690 process specification and the supporting qualification testing. While the testing was able to produce some localized corrosion of alloy 690 in the tube to tubesheet joint transition regions under highly alkaline conditions, the corrosion rates were between two and three orders of magnitude lower than the comparablemore » rates in mill annealed alloy 600 tubing. The corrosion morphology was a combination of intergranular and general corrosion, rather than the stress corrosion cracking typically found in mill annealed alloy 600 tubing.« less

Effect of Temper Condition on the Corrosion and Fatigue Performance of AA2219 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Ghosh, Rahul; Venugopal, A.; Rao, G. Sudarshan; Ramesh Narayanan, P.; Pant, Bhanu; Cherian, Roy M.

2018-02-01

The effect of temper condition and corrosion on the fatigue behavior of alloy AA2219 has been investigated in different temper conditions (T87 and T851). Corrosion testing was performed by exposing the tensile specimens to 3.5% NaCl solution for different time periods, and the corrosion damage was quantified using a 3D profilometer. The exposure-tested specimens were subjected for fatigue testing at different stress levels, and the reduction in fatigue life was measured along with detailed fracture morphology variations. The results indicated that the alloy in both tempers suffers localized corrosion damage and the measured corrosion depth was 120 and 1200 µm, respectively, for T87 and T851 conditions. The loss in fatigue strength was found to be high for T851 (67%) when compared to that of T87 temper condition (58%) for a pre-corrosion time of 15 days. In both cases, fatigue crack initiation is associated with corrosion pits, which act as stress raisers. However, the crack propagation was predominantly transgranular for T87 and a mixed transgranular and intergranular fracture in the case of T851 temper condition. This was shown to be due to the heterogeneous microstructure due to the thermomechanical working and the delay in quench time imposed on the alloy forging in T851 temper condition. The findings in this paper present useful information for the selection of appropriate heat treatment condition to facilitate control of the corrosion behavior which is of great significance for their fatigue performance.

Theoretical aspects of stress corrosion cracking of Alloy 22

NASA Astrophysics Data System (ADS)

Lee, Sang-Kwon; Macdonald, Digby D.

2018-05-01

Theoretical aspects of the stress corrosion cracking of Alloy 22 in contact with saturated NaCl solution are explored in terms of the Coupled Environment Fracture Model (CEFM), which was calibrated upon available experimental crack growth rate data. Crack growth rate (CGR) was then predicted as a function of stress intensity, electrochemical potential, solution conductivity, temperature, and electrochemical crack length (ECL). From the dependence of the CGR on the ECL and the evolution of a semi-elliptical surface crack in a planar surface under constant loading conditions it is predicted that penetration through the 2.5-cm thick Alloy 22 corrosion resistant layer of the waste package (WP) could occur 32,000 years after nucleation. Accordingly, the crack must nucleate within the first 968,000 years of storage. However, we predict that the Alloy 22 corrosion resistant layer will not be penetrated by SCC within the 10,000-year Intermediate Performance Period, even if a crack nucleates immediately upon placement of the WP in the repository.

Physical Metallurgy, Weldability, and in-Service Performance of Nickel-Chromium Filler Metals Used in Nuclear Power Systems

NASA Astrophysics Data System (ADS)

Young, George A.; Etien, Robert A.; Hackett, Micah J.; Tucker, Julie D.; Capobianco, Thomas E.

Wrought Alloy 690 is well established for corrosion resistant nuclear applications but development continues to improve the weldability of a filler metal that retains the corrosion resistance and phase stability of the base metal. High alloy Ni-Cr filler metals are prone to several types of welding defects and new alloys are emerging for commercial use. This paper uses experimental and computational methods to illustrate key differences among welding consumables. Results show that solidification segregation is critical to understanding the weldability and environmentally-assisted cracking resistance of these alloys. Primary water stress corrosion cracking tests show a marked decrease in crack growth rates near 21 wt. % Cr at the grain boundary. While filler metals with 21-29 wt.% grain boundary Cr show similar PWSCC resistance, the higher alloyed grades are more prone to solidification cracking. Modeling and aging studies indicate that in some filler metals minor phase formation (e.g., Laves and σ) and long range order (LRO) must be assessed to ensure adequate weldability and inservice performance.

Effects of hydroxyapatite/Zr and bioglass/Zr coatings on morphology and corrosion behaviour of Rex-734 alloy.

PubMed

Say, Y; Aksakal, B

2016-06-01

To improve corrosion resistance of metallic implant surfaces, Rex-734 alloy was coated with two different bio-ceramics; single-Hydroxyapatite (HA), double-HA/Zirconia(Zr) and double-Bioglass (BG)/Zr by using sol-gel method. Porous surface morphologies at low crack density were obtained after coating and sintering processes. Corrosion characteristics of coatings were determined by Open circuit potential and Potentiodynamic polarization measurements during corrosion tests. Hardness and adhesion strength of coating layers were measured and their surface morphologies before and after corrosion were characterized by scanning electron microscope (SEM), XRD and EDX. Through the SEM analysis, it was observed that corrosion caused degradation and sphere-like formations appeared with dimples on the coated surfaces. The coated substrates that exhibit high crack density, the corrosion was more effective by disturbing and transmitting through the coating layer, produced CrO3 and Cr3O8 oxide formation. It was found that the addition of Zr provided an increase in adhesion strength and corrosion resistance of the coatings. However, BG/Zr coatings had lower adhesion strength than the HA/Zr coatings, but showed higher corrosion resistance.

The stress-corrosion behavior of Al-Li-Cu alloys: A comparison of test methods

NASA Technical Reports Server (NTRS)

Rizzo, P. P.; Galvin, R. P.; Nelson, H. G.

1982-01-01

Two powder metallurgy processed (Al-Li-Cu) alloys with and without Mg addition were studied in aqueous 3.5% NaCl solution during the alternate immersion testing of tuning fork specimens, slow crack growth tests using fracture mechanics specimens, and the slow strain rate testing of straining electrode specimens. Scanning electron microscopy and optical metallography were used to demonstrate the character of the interaction between the Al-Li-Cu alloys and the selected environment. Both alloys are susceptible to SC in an aqueous 3.5% NaCl solution under the right electrochemical and microstructural conditions. Each test method yields important information on the character of the SC behavior. Under all conditions investigated, second phase particles strung out in rows along the extrusion direction in the alloys were rapidly attacked, and played principal role in the SC process. With time, larger pits developed from these rows of smaller pits and under certain electrochemical conditions surface cracks initiated from the larger pits and contributed directly to the fracture process. Evidence to support slow crack growth was observed in both the slow strain rate tests and the sustained immersion tests of precracked fracture mechanics specimens. The possible role of H2 in the stress corrosion cracking process is suggested.

Molten salt corrosion of hot-pressed Si sub 3 N sub 4 /SiC-reinforced composites and effects of molten salt exposure on slow crack growth of hot-pressed Si sub 3 N sub 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henager, C.H. Jr.; Jones, R.H.

1989-11-03

Corrosion and slow crack growth of hot-pressed Si{sub 3}N{sub 4}- based ceramic materials were studied to arrive at an initial determination of the severity of Na{sub 2}SO{sub 4} molten salt environments. Slow crack growth testing revealed that Na{sub 2}SO{sub 4} molten salt exposure accelerated crack growth in hot-pressed Si{sub 3}N{sub 4} compared to crack growth in air at 1300 C. The salt exposure was observed to reduce the time to failure of precracked specimens by factors of two or three. Measured crack velocity was observed to obey a power law, V = AK{sup n}, with n = 5.2 {plus minus}more » 0.2 and A = 7.6 {times} 10{sup {minus}10}. Standard corrosion coupon tests were performed on specimens of Si{sub 3}N{sub 4}/SiC-reinforced composites and hot-pressed Si{sub 3}N{sub 4} monolithic material. Weight change measurements were performed after eight-hour immersion exposures at 950, 975, and 1000 C to Na{sub 2}SO{sub 4}. Hot-pressed Si{sub 3}N{sub 4} + 5% MgO and Si{sub 3}N{sub 4}/SiC whisker-reinforced material exhibited similar surface features after molten salt exposure. A Si{sub 3}N{sub 4}/SiC fiber-reinforced material, however, revealed complete dissolution of SiC chopped fiber reinforcements.« less

Corrosion of post-tensioning strands in ungrouted ducts - unstressed condition

NASA Astrophysics Data System (ADS)

Hutchison, Michael

Recent failures and severe corrosion distress of post-tensioned (PT) bridges in Florida have revealed corrosion of the 7-wire strands in tendons. Post-tensioned duct assemblies are fitted with multiple 7-wire steel strands and ducts are subsequently filled with grout. During construction, the length of time from the moment in which the strands have been inserted into the ducts, until the ducts are grouted, is referred to as the `ungrouted' period. During this phase, the steel strands are vulnerable to corrosion and consequently the length of this period is restricted (typically to 7 days) by construction guidelines. This investigation focuses on determining the extent of corrosion that may take place during that period, but limited to strands that were in the unstressed condition. Visual inspections and tensile testing were used to identify trends in corrosion development. Corrosion induced cracking mechanisms were also investigated via wire bending and metallographic cross section evaluation. Corrosion damage on unstressed strands during ungrouted periods of durations in the order of those otherwise currently prescribed did not appear to seriously degrade mechanical performance as measured by standardized tests. However the presence of stress in the ungrouted period, as is normally the case, may activate other mechanisms (e.g., EAC) that require further investigation. As expected in the unstressed condition, no evidence of transverse cracking was observed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pickman, D.O.

Various aspects of zirconium alloy development for light water reactors in the UK and Scandinavia are reviewed, including the contribution made by some unique nuclear testing facilities. Among the problems encountered were the irradiation enhancement of corrosion and hydrogen pickup, crud deposition, iodine-induced stress-corrosion cracking on power ramping, and severe cladding deformation in loss-of-coolant accident conditions. The causes and behavior of defects, including hydride defects and fretting corrosion, are discussed.

A comparison of constant-load and constant-deflection stress-corrosion tests on precracked DCB specimens. [Double Cantilever Beam

NASA Technical Reports Server (NTRS)

Dorward, R. C.; Hasse, K. R.

1978-01-01

A comparison is made between measurements of stress-corrosion crack propagation made by a constant-load procedure and by a constant-deflection procedure. Precracked double cantilever beam specimens from 7075 aluminum alloy plate were used. The specimens were oriented in such a way that cracking would begin in the short-transverse plane and would propagate in the rolling direction. The specimens were subjected to a buffered salt-chromate solution and a 3.6% synthetic sea salt solution. The measurements were made optically with a binocular microscope. Stress intensities and crack lengths were calculated and crack velocities were obtained. Velocity was plotted against the average calculated stress intensity. Good agreement between the two methods was found for the salt-chromate solution, although some descrepancies were noted for the artificial sea salt solution.

Crack growth testing on Cold Worked Alloy 690 in Primary Water Environment

NASA Astrophysics Data System (ADS)

Tice, David R.; Medway, Stuart L.; Platts, Norman; Stairmand, John W.

While plant experience so far has shown excellent resistance of Alloy 690 to stress corrosion cracking in PWR primary water environments, laboratory tests have reported that susceptibility may be enhanced substantially by non-uniform cold working, particularly when the plane of crack growth is in the plane of rolling or forging. The Alloy 690 program aims to further the understanding of the mechanisms behind this susceptibility and the heat-to-heat variability reported for different materials.

Natural Crack Sizing Based on Eddy Current Image and Electromagnetic Field Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Endo, H.; Uchimoto, T.; Takagi, T.

2006-03-06

An eddy current testing (ECT) system with multi-coil type probes is applied to size up cracks fabricated on austenite stainless plates. We have developed muti-channel ECT system to produce data as digital images. The probes consist of transmit-receive type sensors as elements to classify crack directions, working as two scan direction modes simultaneously. Template matching applied to the ECT images determines regions of interest in sizing up cracks. Finite element based inversion sizes up the crack depth from the measured ECT signal. The present paper demonstrates this approach for fatigue crack and stress corrosion cracking.

ATLAS 60’ Fording Study

DTIC Science & Technology

1992-03-03

crack. Carbon steel stress cracks in the presence of sodium hydroxide (" caustic embrittlement"), whereas austenitic stainless steels stress crack in...transmission life. - Outboard planetary axle design reduces stresses on differential, drive shafts and axle shaft U-joints. . Enclosed oil disc brakes on... Stress Corrosion Crevice Pitting Erosion Corrosion Uniform Corrosion Intergranular Selective Leaching Page 19 Caterpflar Inc. ATLAS Fording Study Q The

Stress Corrosion Cracking Behavior of LD10 Aluminum Alloy in UDMH and N2O4 propellant

NASA Astrophysics Data System (ADS)

Zhang, Youhong; Chang, Xinlong; Liu, Wanlei

2018-03-01

The LD10 aluminum alloy double cantilever beam specimens were corroded under the conditions of Unsymmetric Uimethyl Hydrazine (UDMH), Dinitrogen Tetroxide (N2O4), and 3.5% NaCl environment. The crack propagation behavior of the aluminum alloy in different corrosion environment was analyzed. The stress corrosion cracking behavior of aluminum alloy in N2O4 is relatively slight and there are not evident stress corrosion phenomenons founded in UDMH.

The Delayed Fracture of Aluminum Alloys, End of Year Report.

DTIC Science & Technology

1982-03-01

Corrosion Cracking of Maraging Steel ," Corrosion NACE, 1971, vol. 27, no. 10, pp. 429-433. 17. J.C.M. Li, R.A. Oriani, and L.S. Darken: "The...Park, OH, 1974, p. 274. 32. M.V. Hyatt and M.O. Speidel: Chapter 4 of Stress- Corrosion Cracking in High Strength Steels and in Titanium and Aluminum...reverse side it necessary and identify by block number) Aluminum alloys, stress corrosion cracking, oxide film, Auger electron spectroscopy, Mode I

Study of the fracture kinetics in structural aluminum alloys subjected to a long-term action of a static load and a corrosive medium using specimens of a new type

NASA Astrophysics Data System (ADS)

Kablov, E. N.; Grinevich, A. V.; Lutsenko, A. N.; Erasov, V. S.; Nuzhnyi, G. A.; Gulina, I. V.

2017-04-01

A new type of specimens is proposed to study the fracture kinetics of the metallic materials subjected to a long-term simultaneous action of a tensile load and a corrosive medium. The new design of specimens makes it possible to determine the stress intensity factor at the crack opening fixed by a wedging bolt, to perform investigations in any aggressive medium, and to measure the tensile load on a specimen at any stage of tests. Standard apparatus is used for this purpose. Plate specimens made of structural aluminum alloys 1163T and V95pchT2 are tested. A paradoxical fact of increasing the conventional stress intensity factor of the V95pchT2 alloy during the development of a corrosion crack is revealed.

Use of Marker Bands for Determination of Fatigue Crack Growth Rates and Crack Front Shapes in Pre-Corroded Coupons

NASA Technical Reports Server (NTRS)

Willard, S. A.

1997-01-01

Groups of striations called marker bands generated on a fatigue fracture surface can be used to mark the position of an advancing fatigue crack at known intervals. A technique has been developed that uses the distance between multiple sets of marker bands to obtain a vs. N, crack front shape, and fatigue crack growth rate data for small cracks. This technique is particularly usefull for specimens that require crack length measurements during testing that cannot be obtained because corrosion obscures the surface of the specimen. It is also useful for specimens with unusual or non-symmetric shapes where it is difficult to obtain accurate crack lengths using traditional methods such as compliance or electric potential difference in the early stages of testing.

Corrosion and corrosion fatigue of airframe aluminum alloys

NASA Technical Reports Server (NTRS)

Chen, G. S.; Gao, M.; Harlow, D. G.; Wei, R. P.

1994-01-01

Localized corrosion and corrosion fatigue crack nucleation and growth are recognized as degradation mechanisms that effect the durability and integrity of commercial transport aircraft. Mechanically based understanding is needed to aid the development of effective methodologies for assessing durability and integrity of airframe components. As a part of the methodology development, experiments on pitting corrosion, and on corrosion fatigue crack nucleation and early growth from these pits were conducted. Pitting was found to be associated with constituent particles in the alloys and pit growth often involved coalescence of individual particle-nucleated pits, both laterally and in depth. Fatigue cracks typically nucleated from one of the larger pits that formed by a cluster of particles. The size of pit at which fatigue crack nucleates is a function of stress level and fatigue loading frequency. The experimental results are summarized, and their implications on service performance and life prediction are discussed.

Aqueous sodium chloride induced intergranular corrosion of Al-Li-Cu alloys

NASA Technical Reports Server (NTRS)

Pizzo, P. P.; Daeschner, D. L.

1986-01-01

Two methods have been explored to assess the susceptibility of Al-Li-Cu alloys to intergranular corrosion in aqueous sodium chloride solution. They are: (1) constant extension rate testing with and without alternate-immersion preexposure and (2) metallographic examination after exposure to a NaCl-H2O2 corrosive solution per Mil-H-6088F. Intergranular corrosion was found to occur in both powder and ingot metallurgy alloys of similar composition, using both methods. Underaging rendered the alloys most susceptible. The results correlate to stress-corrosion data generated in conventional time-to-failure and crack growth-rate tests. Alternate-immersion preexposure may be a reliable means to assess stress corrosion susceptibility of Al-Li-Cu alloys.

Effect of NaCl Solution Spraying on Fatigue Lives of Smooth and Slit Specimens of 0.37% Carbon Steel

NASA Astrophysics Data System (ADS)

Makabe, Chobin; Ferdous, Md. Shafiul; Shimabukuro, Akimichi; Murdani, Anggit

2017-07-01

The fatigue crack initiation life and growth rate are affected by experimental conditions. A corrosive environment can be created in a laboratory by means of dropping salt water onto the specimen surface, spraying chloride mist into the experimental chamber, etc. In the case of smooth specimens of some metals, fatigue life is shortened and the fatigue limit disappears under such corrosive experimental conditions. In this study, the effects of intermittent spraying of 3% NaCl solution-mist on corrosion fatigue behavior were investigated. The material used was 0.37% carbon steel. This is called JIS S35C in Japan. Spraying of 3% NaCl solution-mist attacked the surface layer of the specimen. It is well known that the pitting, oxidation-reduction reaction, etc. affect the fatigue strength of metals in a corrosive environment. We carried out corrosion fatigue tests with smooth specimens, holed specimens and slit specimens. Then the effects of such specimen geometry on the fatigue strength were investigated when the NaCl solution-mist was sprayed onto the specimen surface. In the case of lower stress amplitude application in slit specimens, the fatigue life in a corrosive atmosphere was longer than that in the open air. It is discussed that the behavior is related to the crack closure which happens when the oxide builds up and clogs the crack or slit.

75 FR 35356 - Airworthiness Directives; The Boeing Company Model 747-100, 747-200B, and 747-200F Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-22

...-related skin cracks and corrosion of the skin panel lap joints in the fuselage upper lobe, and repair if... inspections of the fuselage skin at the upper lobe skin lap joints for cracks and evidence of corrosion, and... correct fatigue cracking and corrosion in the fuselage upper lobe skin lap joints, which could lead to...

Effect of Localized Corrosion on Fatigue-Crack Growth in 2524-T3 and 2198-T851 Aluminum Alloys Used as Aircraft Materials

NASA Astrophysics Data System (ADS)

Moreto, J. A.; Broday, E. E.; Rossino, L. S.; Fernandes, J. C. S.; Bose Filho, W. W.

2018-03-01

Corrosion and fatigue of aluminum alloys are major issues for the in-service life assessment of aircraft structures and for the management of aging air fleets. The aim of this work was to evaluate the effect of localized corrosion on fatigue crack growth (FCG) resistance of the AA2198-T851 Al-Li alloy (Solution Heat Treated, Cold Worked, and Artificially Aged), comparing it with the FCG resistance of AA2524-T3 (Solution Heat Treated and Cold Worked), considering the effect of seawater fog environment. Before fatigue tests, the corrosion behavior of 2198-T851 and 2524-T3 aluminum alloys was verified using open circuit potential and potentiodynamic polarization techniques. Fatigue in air and corrosion fatigue tests were performed applying a stress ratio (R) of 0.1, 15 Hz (air) and 0.1 Hz (seawater fog) frequencies, using a sinusoidal waveform in all cases. The results showed that the localized characteristics of the 2198-T851 and 2524-T3 aluminum alloys are essentially related to the existence of intermetallic compounds, which, due to their different nature, may be cathodic or anodic in relation to the aluminum matrix. The corrosive medium has affected the FCG rate of both aluminum alloys, in a quite similar way.

Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading

NASA Technical Reports Server (NTRS)

Forman, R. G.; Zanganeh, M.

2014-01-01

This paper describes the results of a research program conducted to improve the understanding of fatigue crack growth rate behavior in the threshold growth rate region and to answer a question on the validity of threshold region test data. The validity question relates to the view held by some experimentalists that using the ASTM load shedding test method does not produce valid threshold test results and material properties. The question involves the fanning behavior observed in threshold region of da/dN plots for some materials in which the low R-ratio data fans out from the high R-ratio data. This fanning behavior or elevation of threshold values in the low R-ratio tests is generally assumed to be caused by an increase in crack closure in the low R-ratio tests. Also, the increase in crack closure is assumed by some experimentalists to result from using the ASTM load shedding test procedure. The belief is that this procedure induces load history effects which cause remote closure from plasticity and/or roughness changes in the surface morphology. However, experimental studies performed by the authors have shown that the increase in crack closure is a result of extensive crack tip bifurcations that can occur in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the fanning behavior which occurs in aluminum alloys is a function of intrinsic dislocation property of the alloy, and therefore, the fanned data does represent the true threshold properties of the material. However, for the corrosion sensitive steel alloys tested in laboratory air, the occurrence of fanning results from fretting corrosion at the crack tips, and these results should not be considered to be representative of valid threshold properties because the fanning is eliminated when testing is performed in dry air.

Corrosion fatigue in nitrocarburized quenched and tempered steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karim Khani, M.; Dengel, D.

1996-05-01

In order to investigate the fatigue strength and fracture mechanism of salt bath nitrocarburized steels, specimens of the steels SAE 4135 and SAE 4140, in a quenched and tempered state, and additionally in a salt bath nitrocarburized and oxidizing cooled state as well as in a polished (after the oxidizing cooling) and renewed oxidized state, were subjected to comparative rotating bending fatigue tests in inert oil and 5 pct NaCl solution. In addition, some of the quenched and tempered specimens of SAE 4135 material were provided with an approximately 50-{mu}m-thick electroless Ni-P layer, in order to compare corrosion fatigue behaviormore » between the Ni-P layer and the nitride layers. Long-life corrosion fatigue tests of SAE 4135 material were carried out under small stresses in the long-life range up to 10{sup 8} cycles with a test frequency of 100 Hz. Fatigue tests of SAE 4140 material were carried out in the range of finite life (low-cycle range) with a test frequency of 13 Hz. The results show that the 5 pct NaCl environment drastically reduced fatigue life, but nitrocarburizing plus oxidation treatment was found to improve the corrosion fatigue life over that of untreated and Ni-P coated specimens. The role of inclusions in initiating fatigue cracks was investigated. It was found that under corrosion fatigue conditions, the fatigue cracks started at cavities along the interfaces of MnS inclusions and matrix in the case of quenched and tempered specimens. The nitrocarburized specimens, however, showed a superposition of pitting corrosion and corrosion fatigue in which pores and nonmetallic inclusions in the compound layer play a predominant role concerning the formation of pits in the substrate.« less

Joining dissimilar stainless steels for pressure vessel components

NASA Astrophysics Data System (ADS)

Sun, Zheng; Han, Huai-Yue

1994-03-01

A series of studies was carried out to examine the weldability and properties of dissimilar steel joints between martensitic and austenitic stainless steels - F6NM (OCr13Ni4Mo) and AISI 347, respectively. Such joints are important parts in, e.g. the primary circuit of a pressurized water reactor (PWR). This kind of joint requires both good mechanical properties, corrosion resistance and a stable magnetic permeability besides good weldability. The weldability tests included weld thermal simulation of the martensitic steel for investigating the influence of weld thermal cycles and post-weld heat treatment (PWHT) on the mechanical properties of the heat-affected zone (HAZ); implant testing for examining the tendency for cold cracking of martensitic steel; rigid restraint testing for determining hot crack susceptibility of the multi-pass dissimilar steel joints. The joints were subjected to various mechanical tests including a tensile test, bending test and impact test at various temperatures, as well as slow strain-rate test for examining the stress corrosion cracking tendency in the simulated environment of a primary circuit of a PWR. The results of various tests indicated that the quality of the tube/tube joints is satisfactory for meeting all the design requirements.

Evaluation of Various Depainting Processes on Mechanical Properties of 2024-T3 Aluminum Substrate

NASA Technical Reports Server (NTRS)

McGill, P.

2001-01-01

Alternate alkaline and neutral chemical paint strippers have been identified that, with respect to corrosion requirements, perform as well as or better than a methylene chloride baseline. These chemicals also, in general, meet corrosion acceptance criteria as specified in SAE MA 4872. Alternate acid chemical paint strippers have been identified that, with respect to corrosion requirements, perform as well as or better than a methylene chloride baseline. However, these chemicals do not generally meet corrosion acceptance criteria as specified in SAE MA 4872, especially in the areas of non-clad material performance and hydrogen embrittlement. Media blast methods reviewed in the study do not, in general, adversely affect fatigue performance or crack detectability of 2024-T3 substrate. Sodium bicarbonate stripping exhibited a tendency towards inhibiting crack detectability. These generalizations are based on a limited sample size and additional testing should be performed to characterize the response of specific substrates to specific processes.

Distributed fiber optic strain sensing to detect artificial pitting corrosion in stirrups

NASA Astrophysics Data System (ADS)

Zhang, Jiachen; Kancharla, Vinutha; Hoult, Neil A.

2017-04-01

Pitting corrosion is difficult to identify through visual inspection and can lead to sudden structural failures. As such, an experimental study was undertaken to investigate whether distributed fiber optic strain sensors are capable of detecting the locations and strain changes associated with stirrup corrosion in reinforced concrete beams. In comparison to conventional strain gauges, this type of sensor can measure the strain response along the entire length of the fiber optic cable. Two specimens were tested: a control and a deteriorated beam. The deteriorated beam was artificially corroded by reducing the cross sectional area of the closed stirrups by 50% on both sides of the stirrup at the mid-height. This level of area reduction represents severe pitting corrosion. The beams were instrumented with nylon coated fiber optic sensors to measure the distributed strains, and then tested to failure under three point bending. The load deflection behavior of the two specimens was compared to assess the impact of the artificial pitting corrosion on the capacity. Digital Image Correlation was used to locate the extent and trajectory of the crack paths. It was found that the pitting corrosion had no impact on capacity or stiffness. Also, in this investigation the fiber optic sensing system failed to detect the location and strain changes due to pitting corrosion since the shear cracks did not intersect with the pitting location.

Corrosion-Fatigue Crack Growth in Plates: A Model Based on the Paris Law

PubMed Central

Toribio, Jesús; Matos, Juan-Carlos; González, Beatriz

2017-01-01

In this paper, a Paris law-based model is presented whereby crack propagation occurs under cyclic loading in air (fatigue) and in an aggressive environment (corrosion-fatigue) for the case of corner cracks (with a wide range of aspect ratios in the matter of the initial cracks) in finite-thickness plates of 316L austenitic stainless steel subjected to tension, bending, or combined (tension + bending) loading. Results show that the cracks tend during their growth towards a preferential propagation path, exhibiting aspect ratios slightly lower than unity only for the case of very shallow cracks, and diminishing as the crack grows (increasing the relative crack depth)—more intensely in the case of bending than in the case of tension (the mixed loading tension/bending representing an intermediate case). In addition, the crack aspect ratios during fatigue propagation evolution are lower in fatigue (in air) than in corrosion-fatigue (in aggressive environment). PMID:28772798

Block 2 solar cell module environmental test program

NASA Technical Reports Server (NTRS)

Holloway, K. L.

1978-01-01

Environmental tests were performed of on 76 solar cell modules produced by four different manufacturers. The following tests were performed: (1) 28 day temperature and humidity; (2) rain and icing; (3) salt fog; (4) sand and dust; (5) vacuum/steam/pressure; (6) fungus; (7) temperature/altitude; and (8) thermal shock. Environmental testing of the solar cell modules produced cracked cells, cracked encapsulant and encapsulant delaminations on various modules. In addition, there was some minor cell and frame corrosion.

Crack Initiation and Growth Behavior at Corrosion Pit in 7075-T6 Under Biaxial and Uniaxial Fatigue

DTIC Science & Technology

2014-06-19

al. examined the effect of biaxial loading on the fatigue crack growth [52]. They conducted their fatigue tests on SUS 304 stainless steel using a...specimens. Their experiments were carried out on cruciform test coupons using a digitally controlled four actuator biaxial testing system. Steel ...as shown in Figure 3.7. The test specimen was placed between two stainless steel chambers. These chambers were connected together using screws, and

Thermal Cycling and High-Temperature Corrosion Tests of Rare Earth Silicate Environmental Barrier Coatings

NASA Astrophysics Data System (ADS)

Darthout, Émilien; Gitzhofer, François

2017-12-01

Lutetium and yttrium silicates, enriched with an additional secondary zirconia phase, environmental barrier coatings were synthesized by the solution precursor plasma spraying process on silicon carbide substrates. A custom-made oven was designed for thermal cycling and water vapor corrosion testing. The oven can test four specimens simultaneously and allows to evaluate environmental barrier performances under similar corrosion kinetics compared to turbine engines. Coatings structural evolution has been observed by SEM on the polished cross sections, and phase composition has been analyzed by XRD. All coatings have been thermally cycled between 1300 °C and the ambient temperature, without spallation, due to their porosity and the presence of additional secondary phase which increases the thermal cycling resistance. During water vapor exposure at 1200 °C, rare earth disilicates showed a good stability, which is contradictory with the literature, due to impurities—such as Si- and Al-hydroxides—in the water vapor jets. The presence of vertical cracks allowed the water vapor to reach the substrate and then to corrode it. It has been observed that thin vertical cracks induced some spallation after 24 h of corrosion.

Variation of the distribution of crack lengths during corrosion fatigue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishihara, S.; Miyao, K.; Shiozawa, K.

1984-07-01

The detailed initiation and growth behaviour of distributed cracks on a specimen surface was investigated during corrosion fatigue. It can be clarified that the changes of the distribution of crack lengths with stress cycling reflect the behaviour of initiation and growth of distributed cracks. The distribution of crack lengths for certain stress cycles could be explained by a statistical calculation which takes into account both the variation of number of cracks during stress cycling and the scatter of crack growth rate.

Thermodynamic analysis on the role of hydrogen in anodic stress corrosion cracking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiao, L.; Mao, X.

1995-11-01

A synergistic effect of hydrogen and stress on a corrosion rate was analyzed with thermodynamics. The results showed that an interaction of stress and hydrogen could increase the corrosion rate remarkably. Stress corrosion cracking (SCC) of austenitic stainless steel (ASS) was investigated in boiling chloride solution to confirm the analysis. Hydrogen could be introduced into the specimen concentrated at the crack tip during SCC in boiling LiCl solution (143 C). The concentrating factor is about 3 which is consistent with calculated results according to stress induced diffusion.

FY17 Status Report: Research on Stress Corrosion Cracking of SNF Interim Storage Canisters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schindelholz, Eric John; Bryan, Charles R.; Alexander, Christopher L.

This progress report describes work done in FY17 at Sandia National Laboratories (SNL) to assess the localized corrosion performance of container/cask materials used in the interim storage of spent nuclear fuel (SNF). Of particular concern is stress corrosion cracking (SCC), by which a through-wall crack could potentially form in a canister outer wall over time intervals that are shorter than possible dry storage times. Work in FY17 refined our understanding of the chemical and physical environment on canister surfaces, and evaluated the relationship between chemical and physical environment and the form and extent of corrosion that occurs. The SNL corrosionmore » work focused predominantly on pitting corrosion, a necessary precursor for SCC, and process of pit-to-crack transition; it has been carried out in collaboration with university partners. SNL is collaborating with several university partners to investigate SCC crack growth experimentally, providing guidance for design and interpretation of experiments.« less

Stress corrosion-controlled rates of mode I fracture propagation in calcareous bedrock

NASA Astrophysics Data System (ADS)

Voigtlaender, Anne; Leith, Kerry; Krautblatter, Michael

2014-05-01

Surface bedrock on natural rock slopes is subject to constant and cyclic environmental stresses (wind, water, wave, ice, seismic or gravitational). Studies indicate that these stresses range up to several hundred kPa, generally too low to cause macroscopic changes in intact rock, although clear evidence of fracture generation, crack propagation and weathering of bedrock illustrates the effect of environmental stresses at the Earth's surface. We suggest that material degradation and its extent, is likely to be controlled by the rate of stress corrosion cracking (SCC). Stress corrosion is a fluid-material reaction, where fluids preferentially react with strained atomic bonds at the tip of developing fractures. Stress corrosion in ferrous and siliceous materials is often accepted as the fracture propagation and degradation rate-controlling process where materials are subject to stresses and fluids. Although evidence for chemical weathering in propagating bedrock fractures is clear in natural environments, the physical system and quantification of stress corrosion in natural rocks is yet to be addressed. Here, we present preliminary data on the relationship between stresses at levels commonly present on natural rock slopes, and material damage resulting from stress corrosion under constant or cyclic tensile loading. We undertake single notch three-point bending tests (SNBT) on fresh calcareous bedrock specimens (1100x100x100mm) over a two-month period. Two beams containing an artificial notch are stressed to 75% of their ultimate strength, and a constant supply of weak acid is applied at the notch tip to enhance chemical reactions. A third, unloaded, beam is also exposed to weak acid in order to elucidate the contribution of stress corrosion cracking to the material degradation. Stresses at the tip of propagating cracks affect the kinetics of the chemical reaction in the specimen exposed to both loading and corrosion, leading to an increase in degradation, and greater stress relaxation. These changes in material properties are monitored using strain gauges, acoustic emission sensors, changes in P-wave velocity, and records of time to failure where appropriate. Our preliminary studies indicate changes in material properties are concentrated in the region of predicted tensile stress intensification. Reactions seem to favourably occur at the stressed bonds around the crack tip. The rate of chemical dissolution and further propagation of the fracture at the notch tip appears to be enhanced by the level of stress applied to the specimen. This provides the foundation for a suite of repeated experiments in which we plan to test corrosion-controlled rates of degradation across a range of loading conditions. The improved understanding into micro-mechanical controls, will contribute to the assessment of rock fall production rates and erosion processes in natural environments as well as natural building stones.

Advanced Cast Aluminum Alloys

DTIC Science & Technology

2009-02-01

This production route has demonstrated that aluminum alloys with yield strengths in excess of 690 MPa with good elongation (reportedly 8%) are...series of aluminum alloys have poor-to-fair general corrosion resistance and poor-to-good stress corrosion cracking resistance. Wrought 2519...aluminum alloy has good strength, good ballistic performance, good stress corrosion cracking resistance but only fair general corrosion resistance

Influence of strain on the corrosion of magnesium alloys and zinc in physiological environments.

PubMed

Törne, Karin; Örnberg, Andreas; Weissenrieder, Jonas

2017-01-15

During implantation load-bearing devices experience stress that may influence its mechanical and corrosion profile and potentially lead to premature rupture. The susceptibility to stress corrosion cracking (SCC) of the Mg-Al alloy AZ61 and Zn was studied in simulated body fluid (m-SBF) and whole blood by slow strain rate (SSR) testing in combination with electrochemical impedance spectroscopy (EIS) and further ex situ analysis including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. AZ61 was found to be highly susceptible to SCC. EIS analysis show that although the majority of cracking occurred during the apparent plastic straining, cracking initiation occurs already in the elastic region at ∼50% of the ultimate tensile strength (UTS). Shifts in EIS phase angle and open circuit potential can be used to detect the onset of SCC. Zinc demonstrated a highly ductile behavior with limited susceptibility to SCC. No significant decrease in UTS was observed in m-SBF but a decrease in time to failure by ∼25% compared to reference samples indicates some effect on the mechanical properties during the ductile straining. The formation of micro cracks, ∼10μm deep, was indicated by the EIS analysis and later confirmed by ex situ SEM. The results of SSR analysis of zinc in whole blood showed a reduced effect compared to m-SBF and no cracks were detected. It appears that formation of an organic surface layer protects the corroding surface from cracking. These results highlight the importance of considering the effect of biological species on the degradation of implants in the clinical situation. Strain may deteriorate the corrosion properties of metallic implants drastically. We study the influence of load on the corrosion properties of a magnesium alloy and zinc by a combination of electrochemical impedance spectroscopy (EIS) and slow strain rate analysis. This combination of techniques has previously not been used for studying degradation in physiological relevant electrolytes. EIS provide valuable information on the initial formation of cracks, detecting crack nucleation before feasible in slow strain rate analysis. This sensitivity of EIS shows the potential for electrochemical methods to be used for in situ monitoring crack formation of implants in more applied studies. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

High-strength bolt corrosion fatigue life model and application.

PubMed

Hui-li, Wang; Si-feng, Qin

2014-01-01

The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life.

Stress Corrosion Cracking Study of Aluminum Alloys Using Electrochemical Noise Analysis

NASA Astrophysics Data System (ADS)

Rathod, R. C.; Sapate, S. G.; Raman, R.; Rathod, W. S.

2013-12-01

Stress corrosion cracking studies of aluminum alloys AA2219, AA8090, and AA5456 in heat-treated and non heat-treated condition were carried out using electrochemical noise technique with various applied stresses. Electrochemical noise time series data (corrosion potential vs. time) was obtained for the stressed tensile specimens in 3.5% NaCl aqueous solution at room temperature (27 °C). The values of drop in corrosion potential, total corrosion potential, mean corrosion potential, and hydrogen overpotential were evaluated from corrosion potential versus time series data. The electrochemical noise time series data was further analyzed with rescaled range ( R/ S) analysis proposed by Hurst to obtain the Hurst exponent. According to the results, higher values of the Hurst exponents with increased applied stresses showed more susceptibility to stress corrosion cracking as confirmed in case of alloy AA 2219 and AA8090.

Tests of NASA ceramic thermal barrier coating for gas-turbine engines

NASA Technical Reports Server (NTRS)

Liebert, C. H.

1979-01-01

A two-layer thermal barrier coating system with a bond coating of nickel-chromium-aluminum-yttrium and a ceramic coating of yttria-stabilized zirconia was tested for corrosion protection, thermal protection and durability. Full-scale gas-turbine engine tests demonstrated that this coating eliminated burning, melting, and warping of uncoated parts. During cyclic corrosion resistance tests made in marine diesel fuel products of combustion in a burner rig, the ceramic cracked on some specimens. Metallographic examination showed no base metal deterioration.

Development of an Accelerated Test Method for the Determination of Susceptibility to Atmospheric Corrosion

NASA Technical Reports Server (NTRS)

Ambrose, John R.

1991-01-01

The theoretical rationale is presented for use of a repetitive cyclic current reversal voltammetric technique for characterization of localized corrosion processes, including atmospheric corrosion. Applicability of this proposed experimental protocol is applied to characterization of susceptibility to crevice and pitting corrosion, atmospheric corrosion and stress corrosion cracking. Criteria upon which relative susceptibility is based were determined and tested using two iron based alloys commonly in use at NASA-Kennedy; A36 (a low carbon steel) and 4130 (a low alloy steel). Practicality of the procedure was demonstrated by measuring changes in anodic polarization behavior during high frequency current reversal cycles of 25 cycles per second with 1 mA/sq cm current density amplitude in solutions containing Cl anions. The results demonstrated that, due to excessive polarization which affects conductivity of barrier corrosion product layers, A36 was less resistant to atmospheric corrosion than its 4130 counterpart; behavior which was also demonstrated during exposure tests.

Corrosion initiation and propagation behavior of corrosion resistant concrete reinforcing materials

NASA Astrophysics Data System (ADS)

Hurley, Michael F.

The life of a concrete structure exposed to deicing compounds or seawater is often limited by chloride induced corrosion of the steel reinforcement. In this study, the key material attributes that affect the corrosion initiation and propagation periods were studied. These included material composition, surface condition, ageing time, propagation behavior during active corrosion, morphology of attack, and type of corrosion products generated by each rebar material. The threshold chloride concentrations for solid 316LN stainless steel, 316L stainless steel clad over carbon steel, 2101 LDX, MMFX-2, and carbon steel rebar were investigated using electrochemical techniques in saturated calcium hydroxide solutions. Surface preparation, test method, duration of period exposed to a passivating condition prior to introduction of chloride, and presence of cladding defects all affected the threshold chloride concentration obtained. A model was implemented to predict the extension of time until corrosion initiation would be expected. 8 years was the predicted time to corrosion initiation for carbon steel. However, model results confirmed that use of 316LN may increase the time until onset of corrosion to 100 years or more. To assess the potential benefits afforded by new corrosion resistant rebar alloys from a corrosion resistance standpoint the corrosion propagation behavior and other factors that might affect the risk of corrosion-induced concrete cracking must also be considered. Radial pit growth was found to be ohmically controlled but repassivation occurred more readily at high potentials in the case of 316LN and 2101 stainless steels. The discovery of ohmically controlled propagation enabled transformation of propagation rates from simulated concrete pore solution to less conductive concrete by accounting for resistance changes in the surrounding medium. The corrosion propagation behavior as well as the morphology of attack directly affects the propensity for concrete cracking. Experimental results were used in conjunction with an existing model to predict the time until concrete cracking occurs for new rebar materials. The results suggest that corrosion resistant materials offer a significant extension to the corrosion propagation stage over carbon steel, even in very aggressive conditions because small, localized anodes develop when initiated.

Chemical effects in the Corrosion of Aluminum and Aluminum Alloys. A Bibliography

DTIC Science & Technology

1976-10-01

tances.II. Effect Of Pomegranate Juice And The Aqueous Extract Of Pomegranate Fruits And Tea leaves On The Corrosion Of Aluminum" The effect of the juices...T7651 tempers to exfoliation and stress- corrosion cracking . 1968-8 D.P. Doyle and H.P. Godard ,a) Tr. Mezhdunar. Kongr. Korroz. Metal, 4, 439-48, (1968...Tapper Brit. Corros. J., 3, 285-87, (1968) "Corrosion Of Aluminum" Summary of the literature of Al corrosion which includes stress- corrosion cracking

Multifrequency Eddy Current Inspection of Corrosion in Clad Aluminum Riveted Lap Joints and Its Effect on Fatigue Life

NASA Astrophysics Data System (ADS)

Okafor, A. C.; Natarajan, S.

2007-03-01

Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency eddy current (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of eddy current inspection, corrosion product removal and fatigue testing are presented.

FUNDAMENTAL PROPERTIES OF ULTRA HIGH PERFORMANCE-STRAIN HARDENING CEMENTITIOUS COMPOSITES AND USAGE FOR REPAIR

NASA Astrophysics Data System (ADS)

Kunieda, Minoru; Shimizu, Kosuke; Eguchi, Teruyuki; Ueda, Naoshi; Nakamura, Hikaru

This paper presents the fundamental properties of Ultra High Performance-Strain Hardening Cementitious Composites (UHP-SHCC), which were depeloped for repair applications. In particular, mechanical properties such as tensile response, shrinkage and bond strength were investigated experimentally. Protective performance of the material such as air permeability, water permeability and penetration of chloride ion was also confirmed comparing to that of ordinary concrete. This paper also introduces the usage of the material in repair of concrete st ructures. Laboratory tests concerining the deterioration induced by corrosion were conducted. The UHP-SHCC that coverd the RC beam resisted not only crack opening along the rebar due to corrosion but also crack opening due to loading tests.

Comparative study: Degree of sensitization and intergranular stress corrosion cracking susceptibility of type 304 stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muraleedharan, P.; Gnanamoorthy, J.B.; Rodriguez, P.

1996-10-01

An attempt was made to correlate the susceptibility of type 304 stainless steel sensitized by isothermal exposures from 500 C to 700 C to intergranular stress corrosion cracking (IGSCC) in boiling 20% sodium chloride solution to the degree of sensitization (DOS) measured using the electrochemical potentiokinetic reactivation (EPR) test. No systematic correlation was detected over the entire time-temperature regime. However, for a given sensitizing temperature, IGSCC susceptibility increased with increasing DOS up to a certain value, with no further increase thereafter. This behavior was attributed to the difference in sensitivities of the EPR and IGSCC tests to chromium depletion atmore » the grain boundaries (GB) during the sensitizing heat treatments.« less

Cyclic fatigue-crack propagation, stress-corrosion, and fracture-toughness behavior in pyrolytic carbon-coated graphite for prosthetic heart valve applications.

PubMed

Ritchie, R O; Dauskardt, R H; Yu, W K; Brendzel, A M

1990-02-01

Fracture-mechanics tests were performed to characterize the cyclic fatigue, stress-corrosion cracking, and fracture-toughness behavior of a pyrolytic carbon-coated graphite composite material used in the manufacture of cardiac valve prostheses. Testing was carried out using compact tension C(T) samples containing "atomically" sharp precracks, both in room-temperature air and principally in a simulated physiological environment of 37 degrees C Ringer's lactate solution. Under sustained (monotonic) loads, the composite exhibited resistance-curve behavior, with a fracture toughness (KIc) between 1.1 and 1.9 MPa square root of m, and subcritical stress-corrosion crack velocities (da/dt) which were a function of the stress intensity K raised to the 74th power (over the range approximately 10(-9) to over 10(-5) m/s). More importantly, contrary to common perception, under cyclic loading conditions the composite was found to display true (cyclic) fatigue failure in both environments; fatigue-crack growth rates (da/dN) were seen to be a function of the 19th power of the stress-intensity range delta K (over the range approximately 10(-11) to over 10(-8) m/cycle). As subcritical crack velocities under cyclic loading were found to be many orders of magnitude faster than those measured under equivalent monotonic loads and to occur at typically 45% lower stress-intensity levels, cyclic fatigue in pyrolytic carbon-coated graphite is reasoned to be a vital consideration in the design and life-prediction procedures of prosthetic devices manufactured from this material.

Bioactive glass-ceramic coating for enhancing the in vitro corrosion resistance of biodegradable Mg alloy

NASA Astrophysics Data System (ADS)

Ye, Xinyu; Cai, Shu; Dou, Ying; Xu, Guohua; Huang, Kai; Ren, Mengguo; Wang, Xuexin

2012-10-01

In this work, a bioactive 45S5 glass-ceramic coating was synthesized on magnesium (Mg) alloy substrate by using a sol-gel dip-coating method, to improve the initial corrosion resistance of AZ31 Mg alloy. The surface morphology and phase composition of the glass-ceramic coating were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The coating composed of amorphous phase and crystalline phase Na2Ca2Si3O9, with the thickness of ∼1.0 μm, exhibited a uniform and crack-free surface morphology. The corrosion behavior of the uncoated and coated Mg alloy substrates was investigated by the electrochemical measurements and immersion tests in simulated body fluid (SBF). Potentiodynamic polarization tests recorded an increase of potential (Ecorr) form -1.60 V to -1.48 V, and a reduction of corrosion current density (icorr) from 4.48 μA cm-2 to 0.16 μA cm-2, due to the protection provided by the glass-ceramic coating. Immersion tests also showed the markedly improved corrosion resistance of the coated sample over the immersion period of 7 days. Moreover, after 14 days of immersion in SBF, the corrosion resistance of the coated sample declined due to the cracking of the glass-ceramic coating, which was confirmed by electrochemical impedance spectroscopy (EIS) analysis. The results suggested that the 45S5 glass-ceramic coated Mg alloy could provide a suitable corrosion behavior for use as degradable implants.

Filler Wire Development for 2195 Aluminum-Lithium. Pt. 2

NASA Technical Reports Server (NTRS)

Bjorkman, Gerald W.; Cho, Alex

1998-01-01

The objective of the research was to determine the susceptibility of submitted welded 2195 plate in an AI (Alternate Immersion) environment. Forty-day AI exposure was completed on 8 welded 2195 stress corrosion samples. No stress corrosion cracking (SCC) was found on any of the samples tested. All 8 samples experienced exfoliation corrosion attack in the heat-affected zone (HAZ) adjacent to the weld. All samples were examined metallographically and showed varying degrees of intergranular corrosion (IG). The filler metal on all samples showed moderate to heavy pitting.

Monitoring corrosion in reinforced concrete structures

NASA Astrophysics Data System (ADS)

Kung, Peter; Comanici, Maria I.

2014-06-01

Many defects can cause deterioration and cracks in concrete; these are results of poor concrete mix, poor workmanship, inadequate design, shrinkage, chemical and environmental attack, physical or mechanical damage, and corrosion of reinforcing steel (RS). We want to develop a suite of sensors and systems that can detect that corrosion is taking place in RS and inform owners how serious the problem is. By understanding the stages of the corrosion process, we can develop special a sensor that detects each transition. First, moisture ingress can be monitored by a fiber optics humidity sensor, then ingress of Chloride, which acts as a catalyst and accelerates the corrosion process by converting iron into ferrous compounds. We need a fiber optics sensor which can quantify Chloride ingress over time. Converting ferric to ferrous causes large volume expansion and cracks. Such pressure build-up can be detected by a fiber optic pressure sensor. Finally, cracks emit acoustic waves, which can be detected by a high frequency sensor made with phase-shifted gratings. This paper will discuss the progress in our development of these special sensors and also our plan for a field test by the end of 2014. We recommend that we deploy these sensors by visually inspecting the affected area and by identifying locations of corrosion; then, work with the designers to identify spots that would compromise the integrity of the structure; finally, drill a small hole in the concrete and insert these sensors. Interrogation can be done at fixed intervals with a portable unit.

78 FR 45845 - Airworthiness Directives; Bell Helicopter Textron Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-30

..., whichever occurs first, cleaning and visually inspecting each T/R blade assembly for a crack, corrosion... be covered under warranty, thereby reducing the cost impact on affected individuals. We do not... a crack, corrosion (may be indicated by blistering, peeling, flaking, bubbling, or cracked paint), a...

Corrosion fatigue in nitrocarburized quenched and tempered steels

NASA Astrophysics Data System (ADS)

Khani, M. Karim; Dengel, D.

1996-05-01

In order to investigate the fatigue strength and fracture mechanism of salt bath nitrocarburized steels, specimens of the steels SAE 4135 and SAE 4140, in a quenched and tempered state, and additionally in a salt bath nitrocarburized and oxidizing cooled state as well as in a polished (after the oxidizing cooling) and renewed oxidized state, were subjected to comparative rotating bending fatigue tests in inert oil and 5 pct NaCl solution. In addition, some of the quenched and tempered specimens of SAE 4135 material were provided with an approximately 50-μm-thick electroless Ni-P layer, in order to compare corrosion fatigue behavior between the Ni-P layer and the nitride layers. Long-life corrosion fatigue tests of SAE 4135 material were carried out under small stresses in the long-life range up to 108 cycles with a test frequency of 100 Hz. Fatigue tests of SAE 4140 material were carried out in the range of finite life (low-cycle range) with a test frequency of 13 Hz. The results show that the 5 pct NaCl environment drastically reduced fatigue life, but nitrocarburizing plus oxidation treatment was found to improve the corrosion fatigue life over that of untreated and Ni-P coated specimens. The beneficial effect of nitrocarburizing followed by oxidation treatment on cor-rosion fatigue life results from the protection rendered by the compound layer by means of a well-sealed oxide layer, whereby the pores present in the compound layer fill up with oxides. The role of inclusions in initiating fatigue cracks was investigated. It was found that under corrosion fatigue conditions, the fatigue cracks started at cavities along the interfaces of MnS inclusions and matrix in the case of quenched and tempered specimens. The nitrocarburized specimens, however, showed a superposition of pitting corrosion and corrosion fatigue in which pores and nonmetallic inclusions in the compound layer play a predominant role concerning the formation of pits in the substrate.

DOUBLE SHELL TANK (DST) INTEGRITY PROJECT HIGH LEVEL WASTE CHEMISTRY OPTIMIZATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

WASHENFELDER DJ

2008-01-22

The U.S. Department of Energy's Office (DOE) of River Protection (ORP) has a continuing program for chemical optimization to better characterize corrosion behavior of High-Level Waste (HLW). The DOE controls the chemistry in its HLW to minimize the propensity of localized corrosion, such as pitting, and stress corrosion cracking (SCC) in nitrate-containing solutions. By improving the control of localized corrosion and SCC, the ORP can increase the life of the Double-Shell Tank (DST) carbon steel structural components and reduce overall mission costs. The carbon steel tanks at the Hanford Site are critical to the mission of safely managing stored HLWmore » until it can be treated for disposal. The DOE has historically used additions of sodium hydroxide to retard corrosion processes in HLW tanks. This also increases the amount of waste to be treated. The reactions with carbon dioxide from the air and solid chemical species in the tank continually deplete the hydroxide ion concentration, which then requires continued additions. The DOE can reduce overall costs for caustic addition and treatment of waste, and more effectively utilize waste storage capacity by minimizing these chemical additions. Hydroxide addition is a means to control localized and stress corrosion cracking in carbon steel by providing a passive environment. The exact mechanism that causes nitrate to drive the corrosion process is not yet clear. The SCC is less of a concern in the newer stress relieved double shell tanks due to reduced residual stress. The optimization of waste chemistry will further reduce the propensity for SCC. The corrosion testing performed to optimize waste chemistry included cyclic potentiodynamic volarization studies. slow strain rate tests. and stress intensity factor/crack growth rate determinations. Laboratory experimental evidence suggests that nitrite is a highly effective:inhibitor for pitting and SCC in alkaline nitrate environments. Revision of the corrosion control strategies to a nitrite-based control, where there is no constant depletion mechanism as with hydroxide, should greatly enhance tank lifetime, tank space availability, and reduce downstream reprocessing costs by reducing chemical addition to the tanks.« less

Corrosion, stress corrosion cracking, and electrochemistry of the iron and nickel base alloys in caustic environments. Progress report, 1 March 1977--28 February 1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staehle, R.W.; Agrawal, A.K.

1978-01-01

The straining electrode technique was used to evaluate the stress corrosion cracking (SCC) susceptibility of AISI 304 stainless steel in 20N NaOH solution, and of Inconel 600 Alloy and Incoloy 800 Alloy in boiling 17.5N NaOH solution. The crack propagation rate estimated from the straining experiments correlated well with the previous constant load experiments. It was found that the straining electrode technique is a useful method for estimating, through short term experiments, parameters like crack propagation rate, crack morphology, and repassivation rate, as a function of the electrode potential. The role of alloying elements on the crack propagation rate inmore » the above alloys are also discussed.« less

In situ investigation of high humidity stress corrosion cracking of 7075 aluminum alloy by three-dimensional (3D) X-ray synchrotron tomography

DOE PAGES

Singh, S. S.; Williams, J. J.; Lin, M. F.; ...

2014-05-14

In situ X-ray synchrotron tomography was used to investigate the stress corrosion cracking behavior of under-aged Al–Zn–Mg–Cu alloy in moisture. The discontinuous surface cracks (crack jumps) mentioned in the literature are actually a single continuous and tortuous crack when observed in three dimension (3D). Contrary to 2D measurements made at the surface which suggest non-uniform crack growth rates, 3D measurements of the crack length led to a much more accurate measurement of crack growth rates.

Corrosion-Fatigue Cracking in HY-80 and HY-130 Steels

DTIC Science & Technology

2015-01-22

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6355--15-9584 Corrosion- Fatigue Cracking in HY-80 and HY-130 Steels January 22, 2015 P.S...RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (include area code) b. ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Corrosion- Fatigue ...including [NaCl] concentration) and load ratio on fatigue crack growth kinetics of HY-80 and HY-130 steels. Fracture mechanics wedge-opening-load

76 FR 72863 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-28

... discrepancies if necessary. This proposed AD was prompted by reports of stress corrosion cracking in the chord... segments made from 7075 aluminum. We are proposing this AD to detect and correct stress corrosion and/or... proposed AD. Discussion We have received numerous reports of stress corrosion cracking in the chord...

78 FR 49978 - Airworthiness Directives; the Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-16

... currently requires repetitive inspections for cracking and corrosion of the aft pressure bulkhead, and... we issued AD 2002-10-11, we have received three reports of severe corrosion in the area affected by... actions if necessary. This proposed AD would also limit corrosion and cracking repairs of the aft pressure...

77 FR 26156 - Airworthiness Directives; Cessna Aircraft Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-03

... surrounding components (wheel base, side rim, lock ring) for damage (such as corrosion, cracks, dents, bent areas, damaged or missing paint or primer, or wear on the metal), and of the bearing cup for corrosion... and surrounding components (wheel base, side rim, lock ring) for damage (such as corrosion, cracks...

Selective Internal Oxidation as a Mechanism for Intergranular Stress Corrosion Cracking of Ni-Cr-Fe Alloys

NASA Astrophysics Data System (ADS)

Capell, Brent M.; Was, Gary S.

2007-06-01

The mechanism of selective internal oxidation (SIO) for intergranular stress corrosion cracking (IGSCC) of nickel-base alloys has been investigated through a series of experiments using high-purity alloys and a steam environment to control the formation of NiO on the surface. Five alloys (Ni-9Fe, Ni-5Cr, Ni-5Cr-9Fe, Ni-16Cr-9Fe, and Ni-30Cr-9Fe) were used to investigate oxidation and intergranular cracking behavior for hydrogen-to-water vapor partial pressure ratios (PPRs) between 0.001 and 0.9. The Ni-9Fe, Ni-5Cr, and Ni-5Cr-9Fe alloys formed a uniform Ni(OH)2 film at PPRs less than 0.09, and the higher chromium alloys formed chromium-rich oxide films over the entire PPR range studied. Corrosion coupon results show that grain boundary oxides extended for significant depths (>150 nm) below the sample surface for all but the highest Cr containing alloy. Constant extension rate tensile (CERT) test results showed that intergranular cracking varied with PPR and cracking was more pronounced at a PPR value where nonprotective Ni(OH)2 was able to form and a link between the nonprotective Ni(OH)2 film and the formation of grain boundary oxides is suggested. The observation of grain boundary oxides in stressed and unstressed samples as well as the influence of alloy content on IG cracking and oxidation support SIO as a mechanism for IGSCC.

Assessment of corrosion fatigue damage by acoustic emission and periodic proof tests

NASA Astrophysics Data System (ADS)

Mehdizadeh, P.

1976-03-01

The development of a better nondestructive inspection method for detecting corrosion fatigue damage based on acoustic emission (AE) and periodic proof testing (PPT) is studied for corrosion fatigue tests in salt water solution under tension-tension loading. It is shown that PPT combined with AE monitoring can be a sensitive method for assessing the progress of corrosion fatigue damage as the continuous AE monitoring method. The AE-PPT technique is shown to be dependent on the geometry and size of the crack relative to the test specimen. A qualitative method based on plateauing of acoustic emission counts during proof tests due to changes in the fracture mode is used to predict the remaining fatigue life up to 70% of the actual values. PPT is shown to have no adverse effect on fatigue performance in salt water.

Double torsion fracture mechanics testing of shales under chemically reactive conditions

NASA Astrophysics Data System (ADS)

Chen, X.; Callahan, O. A.; Holder, J. T.; Olson, J. E.; Eichhubl, P.

2015-12-01

Fracture properties of shales is vital for applications such as shale and tight gas development, and seal performance of carbon storage reservoirs. We analyze the fracture behavior from samples of Marcellus, Woodford, and Mancos shales using double-torsion (DT) load relaxation fracture tests. The DT test allows the determination of mode-I fracture toughness (KIC), subcritical crack growth index (SCI), and the stress-intensity factor vs crack velocity (K-V) curves. Samples are tested at ambient air and aqueous conditions with variable ionic concentrations of NaCl and CaCl2, and temperatures up to 70 to determine the effects of chemical/environmental conditions on fracture. Under ambient air condition, KIC determined from DT tests is 1.51±0.32, 0.85±0.25, 1.08±0.17 MPam1/2 for Marcellus, Woodford, and Mancos shales, respectively. Tests under water showed considerable change of KIC compared to ambient condition, with 10.6% increase for Marcellus, 36.5% decrease for Woodford, and 6.7% decrease for Mancos shales. SCI under ambient air condition is between 56 and 80 for the shales tested. The presence of water results in a significant reduction of the SCI from 70% to 85% compared to air condition. Tests under chemically reactive solutions are currently being performed with temperature control. K-V curves under ambient air conditions are linear with stable SCI throughout the load-relaxation period. However, tests conducted under water result in an initial cracking period with SCI values comparable to ambient air tests, which then gradually transition into stable but significantly lower SCI values of 10-20. The non-linear K-V curves reveal that crack propagation in shales is initially limited by the transport of chemical agents due to their low permeability. Only after the initial cracking do interactions at the crack tip lead to cracking controlled by faster stress corrosion reactions. The decrease of SCI in water indicates higher crack propagation velocity due to faster stress corrosion rate in water than in ambient air. The experimental results are applicable for the prediction of fracture initiation based on KIC, modeling fracture pattern based on SCI, and the estimation of dynamic fracture propagation such as crack growth velocity and crack re-initiation.

Hanford Double Shell Waste Tank Corrosion Studies - Final Report FY2015

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuentes, R. E.; Wyrwas, R. B.

2016-05-01

During FY15, SRNL performed corrosion testing that supported Washington River Protection Solutions (WRPS) with their double shell tank (DST) integrity program. The testing investigated six concerns including, 1) the possibility of corrosion of the exterior of the secondary tank wall; 2) the effect of ammonia on vapor space corrosion (VSC) above waste simulants; 3) the determination of the minimum required nitrite and hydroxide concentrations that prevent pitting in concentrated nitrate solutions (i.e., waste buffering); 4) the susceptibility to liquid air interface (LAI) corrosion at proposed stress corrosion cracking (SCC) inhibitor concentrations; 5) the susceptibility of carbon steel to pitting inmore » dilute solutions that contain significant quantities of chloride and sulfate; and 6) the effect of different heats of A537 carbon steel on the corrosion response. For task 1, 2, and 4, the effect of heat treating and/ or welding of the materials was also investigated.« less

Prediction of residual shear strength of corroded reinforced concrete beams

NASA Astrophysics Data System (ADS)

Imam, Ashhad; Azad, Abul Kalam

2016-09-01

With the aim of providing experimental data on the shear capacity and behavior of corroded reinforced concrete beams that may help in the development of strength prediction models, the test results of 13 corroded and four un-corroded beams are presented. Corrosion damage was induced by accelerated corrosion induction through impressed current. Test results show that loss of shear strength of beams is mostly attributable to two important damage factors namely, the reduction in stirrups area due to corrosion and the corrosion-induced cracking of concrete cover to stirrups. Based on the test data, a method is proposed to predict the residual shear strength of corroded reinforced concrete beams in which residual shear strength is calculated first by using corrosion-reduced steel area alone, and then it is reduced by a proposed reduction factor, which collectively represents all other applicable corrosion damage factors. The method seems to yield results that are in reasonable agreement with the available test data.

Accelerated Stress Corrosion Crack Initiation of Alloys 600 and 690 in Hydrogenated Supercritical Water

NASA Astrophysics Data System (ADS)

Moss, Tyler; Was, Gary S.

2017-04-01

The objective of this study is to determine whether stress corrosion crack initiation of Alloys 600 and 690 occurs by the same mechanism in subcritical and supercritical water. Tensile bars of Alloys 690 and 600 were strained in constant extension rate tensile experiments in hydrogenated subcritical and supercritical water from 593 K to 723 K (320 °C to 450 °C), and the crack initiation behavior was characterized by high-resolution electron microscopy. Intergranular cracking was observed across the entire temperature range, and the morphology, structure, composition, and temperature dependence of initiated cracks in Alloy 690 were consistent between hydrogenated subcritical and supercritical water. Crack initiation of Alloy 600 followed an Arrhenius relationship and did not exhibit a discontinuity or change in slope after crossing the critical temperature. The measured activation energy was 121 ± 13 kJ/mol. Stress corrosion crack initiation in Alloy 690 was fit with a single activation energy of 92 ± 12 kJ/mol across the entire temperature range. Cracks were observed to propagate along grain boundaries adjacent to chromium-depleted metal, with Cr2O3 observed ahead of crack tips. All measures of the SCC behavior indicate that the mechanism for stress corrosion crack initiation of Alloy 600 and Alloy 690 is consistent between hydrogenated subcritical and supercritical water.

Quantification of the Service Life Extension and Environmental Benefit of Chloride Exposed Self-Healing Concrete.

PubMed

Van Belleghem, Bjorn; Van den Heede, Philip; Van Tittelboom, Kim; De Belie, Nele

2016-12-23

Formation of cracks impairs the durability of concrete elements. Corrosion inducing substances, such as chlorides, can enter the matrix through these cracks and cause steel reinforcement corrosion and concrete degradation. Self-repair of concrete cracks is an innovative technique which has been studied extensively during the past decade and which may help to increase the sustainability of concrete. However, the experiments conducted until now did not allow for an assessment of the service life extension possible with self-healing concrete in comparison with traditional (cracked) concrete. In this research, a service life prediction of self-healing concrete was done based on input from chloride diffusion tests. Self-healing of cracks with encapsulated polyurethane precursor formed a partial barrier against immediate ingress of chlorides through the cracks. Application of self-healing concrete was able to reduce the chloride concentration in a cracked zone by 75% or more. As a result, service life of steel reinforced self-healing concrete slabs in marine environments could amount to 60-94 years as opposed to only seven years for ordinary (cracked) concrete. Subsequent life cycle assessment calculations indicated important environmental benefits (56%-75%) for the ten CML-IA (Center of Environmental Science of Leiden University-Impact Assessment) baseline impact indicators which are mainly induced by the achievable service life extension.

Factors affecting stress assisted corrosion cracking of carbon steel under industrial boiler conditions

NASA Astrophysics Data System (ADS)

Yang, Dong

Failure of carbon steel boiler tubes from waterside has been reported in the utility boilers and industrial boilers for a long time. In industrial boilers, most waterside tube cracks are found near heavy attachment welds on the outer surface and are typically blunt, with multiple bulbous features indicating a discontinuous growth. These types of tube failures are typically referred to as stress assisted corrosion (SAC). For recovery boilers in the pulp and paper industry, these failures are particularly important as any water leak inside the furnace can potentially lead to smelt-water explosion. Metal properties, environmental variables, and stress conditions are the major factors influencing SAC crack initation and propagation in carbon steel boiler tubes. Slow strain rate tests (SSRT) were conducted under boiler water conditions to study the effect of temperature, oxygen level, and stress conditions on crack initation and propagation on SA-210 carbon steel samples machined out of boiler tubes. Heat treatments were also performed to develop various grain size and carbon content on carbon steel samples, and SSRTs were conducted on these samples to examine the effect of microstructure features on SAC cracking. Mechanisms of SAC crack initation and propagation were proposed and validated based on interrupted slow strain tests (ISSRT). Water chemistry guidelines are provided to prevent SAC and fracture mechanics model is developed to predict SAC failure on industrial boiler tubes.

Stress Corrosion Cracking Behavior of Interstitial Free Steel Via Slow Strain Rate Technique

NASA Astrophysics Data System (ADS)

Murkute, Pratik; Ramkumar, J.; Mondal, K.

2016-07-01

An interstitial free steel is subjected to slow strain rate tests to investigate the stress corrosion cracking (SCC) behavior at strain rates ranging from 10-4 to 10-6s-1 in air and 3.5 wt.% NaCl solution. The ratios of time to failure, failure strain, and ultimate tensile stress at different strain rates in air to that in corrosive were considered as SCC susceptibility. Serrated stress-strain curve observed at lowest strain rate is explained by the Portevin-Le Chatelier effect. Maximum susceptibility to SCC at lowest strain rate is attributed to the soluble γ-FeOOH in the rust analyzed by Fourier Transformed Infrared spectroscopy. Mechanism for SCC relates to the anodic dissolution forming the groove, where hydrogen embrittlement can set in and finally fracture happens due to triaxiality.

78 FR 65204 - Airworthiness Directives; BAE Systems (Operations) Limited Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-31

... the number 1 engine due to stress corrosion. This AD requires repetitive inspections and, depending on.... Subsequent investigation revealed that the cause of cracking was stress corrosion. Cracking of the pylon pick... bracket of the forward outboard pylon of the number 1 engine due to stress corrosion. We are issuing this...

49 CFR 192.923 - How is direct assessment used and for what threats?

Code of Federal Regulations, 2011 CFR

2011-10-01

... Transmission Pipeline Integrity Management § 192.923 How is direct assessment used and for what threats? (a... corrosion (ICDA), and stress corrosion cracking (SCCDA). (b) Primary method. An operator using direct..., appendix A3, and § 192.929 if addressing stress corrosion cracking (SCCDA). (c) Supplemental method. An...

49 CFR 192.923 - How is direct assessment used and for what threats?

Code of Federal Regulations, 2013 CFR

2013-10-01

... Transmission Pipeline Integrity Management § 192.923 How is direct assessment used and for what threats? (a... corrosion (ICDA), and stress corrosion cracking (SCCDA). (b) Primary method. An operator using direct..., appendix A3, and § 192.929 if addressing stress corrosion cracking (SCCDA). (c) Supplemental method. An...

49 CFR 192.923 - How is direct assessment used and for what threats?

Code of Federal Regulations, 2012 CFR

2012-10-01

... Transmission Pipeline Integrity Management § 192.923 How is direct assessment used and for what threats? (a... corrosion (ICDA), and stress corrosion cracking (SCCDA). (b) Primary method. An operator using direct..., appendix A3, and § 192.929 if addressing stress corrosion cracking (SCCDA). (c) Supplemental method. An...

49 CFR 192.923 - How is direct assessment used and for what threats?

Code of Federal Regulations, 2014 CFR

2014-10-01

... Transmission Pipeline Integrity Management § 192.923 How is direct assessment used and for what threats? (a... corrosion (ICDA), and stress corrosion cracking (SCCDA). (b) Primary method. An operator using direct..., appendix A3, and § 192.929 if addressing stress corrosion cracking (SCCDA). (c) Supplemental method. An...

76 FR 721 - Airworthiness Directives; Gulfstream Aerospace Corporation Model G-1159 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-06

... requires an inspection to detect cracks or corrosion in the wing structure in the area of Fuselage Station... required repetitive inspections to detect corrosion or cracks in the forward and aft wing attach fittings...; and the application of corrosion protection treatment. Since the issuance of the NPRM, the Federal...

Influence of localized deformation on A-286 austenitic stainless steel stress corrosion cracking in PWR primary water

NASA Astrophysics Data System (ADS)

Fournier, L.; Savoie, M.; Delafosse, D.

2007-06-01

The low cycle fatigue (LCF) behaviour of precipitation-strengthened A-286 austenitic stainless steel was first investigated at room temperature under 0.2% plastic strain control. LCF led to hardening for the first 20 cycles and then to significant softening. LCF-induced dislocation microstructure was characterized using both bright and dark-field imaging techniques in transmission electron microscopy. Cycling softening was correlated with the formation of precipitate-free localized deformation bands. The effect of these precipitate-free localized deformation bands on A-286 stress corrosion cracking (SCC) behaviour in PWR primary water was then examined by means of constant extension rate tensile (CERT) tests at 320 °C and 360 °C. Comparative CERT tests were performed on companion specimens with similar yield stress but pre-fatigued to a few cycles (4-8) or between 125 and 200 cycles. Specimens pre-fatigued to a few cycles with no precipitate-free localized deformation bands exhibited little susceptibility to intergranular SCC (IGSCC). In contrast, the presence of precipitate-free localized deformation bands formed by pre-fatigue to between 125 and 200 cycles strongly promoted IGSCC. The interest of the approach used in this study is to provide insight into the role of localized deformation in irradiation assisted stress corrosion cracking.

Evolution of Microstructure and Stress Corrosion Cracking Behavior of AA2219 Plate to Ring Weld Joints in 3.5 Wt Pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Narayanan, P. Ramesh; Sharma, S. C.

2016-04-01

AA2219 aluminum alloy plate (T87) and ring (T851) were joined by tungsten inert gas (TIG) welding using multi-pass welding. The mechanical properties and stress corrosion cracking (SCC) resistance of the above base metals (BMs) in different directions (L, LT, and ST) were examined. Similarly, the weld metal joined by plate to plate and plate to ring (PR) joints was evaluated. The results revealed that the mechanical properties of the ring were comparatively lower than the plate. This was found to be due to the extremely coarse grain size of the ring along with severe Cu-rich segregation along the grain boundaries when compared to the plate material. The SCC resistance of the base and weldments were found to be good and not susceptible to SCC. This was shown to be due to high values of SCC index (>0.9) and the typical ductile cracking morphology of the BM and the weld joints after SCC test in the environment (3.5 wt pct NaCl) when compared to test performed in the control environment (air). However, the corrosion resistance of the weld interface between the FZ and ring was inferior to the FZ-plate interface.

77 FR 36127 - Airworthiness Directives; BAE SYSTEMS (Operations) Limited Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-18

... by reports of cracking found in the wing rear spar. This AD requires a one-time detailed inspection for cracks, corrosion, and other defects of the rear face of the wing rear spar, and repair if...] AD requires a one- time [detailed] inspection [for cracks, corrosion, and other defects] of the rear...

78 FR 11972 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-21

... cracks in the skin and surrounding structure under the number 3 very high frequency (VHF) antenna on the.... This AD requires inspecting for cracking and corrosion under the number 3 VHF antenna, and corrective... cracks and corrosion of the skin and surrounding structure under the number 3 VHF antenna, which could...

Magnesium alloys as body implants: fracture mechanism under dynamic and static loadings in a physiological environment.

PubMed

Choudhary, Lokesh; Raman, R K Singh

2012-02-01

It is essential that a metallic implant material possesses adequate resistance to cracking/fracture under the synergistic action of a corrosive physiological environment and mechanical loading (i.e. stress corrosion cracking (SCC)), before the implant can be put to actual use. This paper presents a critique of the fundamental issues with an assessment of SCC of a rapidly corroding material such as magnesium alloys, and describes an investigation into the mechanism of SCC of a magnesium alloy in a physiological environment. The SCC susceptibility of the alloy in a simulated human body fluid was established by slow strain rate tensile (SSRT) testing using smooth specimens under different electrochemical conditions for understanding the mechanism of SCC. However, to assess the life of the implant devices that often possess fine micro-cracks, SCC susceptibility of notched specimens was investigated by circumferential notch tensile (CNT) testing. CNT tests also produced important design data, i.e. threshold stress intensity for SCC (KISCC) and SCC crack growth rate. Fractographic features of SCC were examined using scanning electron microscopy. The SSRT and CNT results, together with fractographic evidence, confirmed the SCC susceptibility of both smooth and notched specimens of a magnesium alloy in the physiological environment. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Microstructural investigation of vintage pipeline steels highly susceptible to stress corrosion cracking

NASA Astrophysics Data System (ADS)

Torres, Monica

The use of pipelines for the transmission of gas offers not only efficiency, but a number of economic advantages. Nevertheless, pipelines are subject to aggressive operating conditions and environments which can lead to in-service degradation [1] and thus to failures. These failures can have catastrophic consequences, such as environmental damage and loss of life [2]. One of the most dangerous threats to pipeline integrity is stress corrosion cracking (SCC). Despite the substantial progress that has been achieved in the field, due to the complex nature of this phenomenon there is still not a complete understanding of this form of external corrosion. This makes its detection and prevention a challenge and therefore a risk to pipeline integrity, and most importantly, to the safety of the population. SCC cracks are the result of the interaction between a corrosive environment, applied stresses, and a susceptible microstructure. To date, what defines a susceptible microstructure remains ambiguous, as SCC has been observed in a range of steel grades, microstructures, chemical composition, and grain sizes. Therefore, in order to be able to accurately predict and prevent this hazardous form of corrosion, it is imperative to advance our knowledge on the subject and gain a better understanding on the microstructural features of highly susceptible pipeline materials, especially in the subsurface zone where crack nucleation must take place. Therefore, a microstructural characterization of the region near the surface layer was carried-out utilizing TEM. TEM analysis revealed the dislocation character, ferrite morphology, and apparent carbide precipitation in some grain boundaries. Furthermore, light microscopy, SEM, and hardness testing were performed to expand our knowledge on the microscopical features of highly SCC susceptible service components. This investigation presents a new approach to SCC characterization, which exposed the sub-surface region microscopical characteristics of service components with confirmed SCC.

Sulfide Stress Cracking and Electrochemical Corrosion of Precipitation Hardening Steel After Plasma Oxy-Nitriding

NASA Astrophysics Data System (ADS)

Granda-Gutiérrez, E. E.; Díaz-Guillén, J. C.; Díaz-Guillén, J. A.; González, M. A.; García-Vázquez, F.; Muñóz, R.

2014-11-01

In this paper, we present the results of a duplex plasma nitriding followed by an oxidizing stage process (which is also referred as oxy-nitriding) on the corrosion behavior of a 17-4PH precipitation hardening stainless steel. The formation of both, expanded martensite (b.c.t. α'N-phase) and chromium oxide (type Cr2O3) in the subsurface of oxy-nitrided samples at specific controlled conditions, leads in a noticeable increasing in the time-to-rupture during the sulfide stress cracking test, in comparison with an untreated reference sample. Oxy-nitriding improves the corrosion performance of the alloy when it is immersed in solutions saturated by sour gas, which extends the application potential of this type of steel in the oil and gas extraction and processing industry. The presence of the oxy-nitrided layer inhibits the corrosion process that occurs in the near-surface region, where hydrogen is liberated after the formation of iron sulfides, which finally produces a fragile fracture by micro-crack propagation; the obtained results suggest that oxy-nitriding slows this process, thus delaying the rupture of the specimen. Moreover, oxy-nitriding produces a hard, sour gas-resistant surface, but do not significantly affect the original chloride ion solution resistance of the material.

Three-dimensional study of grain boundary engineering effects on intergranular stress corrosion cracking of 316 stainless steel in high temperature water

NASA Astrophysics Data System (ADS)

Liu, Tingguang; Xia, Shuang; Bai, Qin; Zhou, Bangxin; Zhang, Lefu; Lu, Yonghao; Shoji, Tetsuo

2018-01-01

The intergranular cracks and grain boundary (GB) network of a GB-engineered 316 stainless steel after stress corrosion cracking (SCC) test in high temperature high pressure water of reactor environment were investigated by two-dimensional and three-dimensional (3D) characterization in order to expose the mechanism that GB-engineering mitigates intergranular SCC. The 3D microstructure shown that the essential characteristic of the GB-engineered microstructure is formation of many large twin-boundaries as a result of multiple-twinning, which results in the formation of large grain-clusters. The large grain-clusters played a key role to the improvement of intergranular SCC resistance by GB-engineering. The main intergranular cracks propagated in a zigzag along the outer boundaries of these large grain-clusters because all inner boundaries of the grain-clusters were twin-boundaries (∑3) or twin-related boundaries (∑3n) which had much lower susceptibility to SCC than random boundaries. These large grain-clusters had tree-ring-shaped topology structure and very complex morphology. They got tangled so that difficult to be separated during SCC, resulting in some large crack-bridges retained in the crack surface.

EVALUATION OF THE MECHANICAL PROPERTIES OF 9NI-4CO FORGINGS.

DTIC Science & Technology

FORGING, MECHANICAL PROPERTIES, STEEL , QUENCHING, SPECIFICATIONS, TENSILE PROPERTIES, COMPRESSIVE PROPERTIES, FATIGUE(MECHANICS), TOUGHNESS, STRESS...CORROSION, THERMAL STABILITY, STRAIN(MECHANICS), BAINITE , TEST METHODS, HEAT TREATMENT, CRACK PROPAGATION.

Stainless and Galvanized Steel, Hydrophobic Admixture and Flexible Polymer-Cement Coating Compared in Increasing Durability of Reinforced Concrete Structures

NASA Astrophysics Data System (ADS)

Tittarelli, Francesca; Giosuè, Chiara; Mobili, Alessandra

2017-08-01

The use of stainless or galvanized steel reinforcements, a hydrophobic admixture or a flexible polymer-cement coating were compared as methods to improve the corrosion resistance of sound or cracked reinforced concrete specimens exposed to chloride rich solutions. The results show that in full immersion condition, negligible corrosion rates were detected in all cracked specimens, except those treated with the flexible polymer-cement mortar as preventive method against corrosion and the hydrophobic concrete specimens. High corrosion rates were measured in all cracked specimens exposed to wet-dry cycles, except for those reinforced with stainless steel, those treated with the flexible polymer-cement coating as restorative method against reinforcement corrosion and for hydrophobic concrete specimens reinforced with galvanized steel reinforcements.

Characterization of cracking behavior using posttest fractographic analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, T.; Shockey, D.A.

A determination of time to initiation of stress corrosion cracking in structures and test specimens is important for performing structural failure analysis and for setting inspection intervals. Yet it is seldom possible to establish how much of a component's lifetime represents the time to initiation of fracture and how much represents postinitiation crack growth. This exploratory research project was undertaken to examine the feasibility of determining crack initiation times and crack growth rates from posttest examination of fracture surfaces of constant-extension-rate-test (CERT) specimens by using the fracture reconstruction applying surface topography analysis (FRASTA) technique. The specimens used in this studymore » were Type 304 stainless steel fractured in several boiling water reactor (BWR) aqueous environments. 2 refs., 25 figs., 2 tabs.« less

A test procedure for determining the influence of stress ratio on fatigue crack growth

NASA Technical Reports Server (NTRS)

Fitzgerald, J. H.; Wei, R. P.

1974-01-01

A test procedure is outlined by which the rate of fatigue crack growth over a range of stress ratios and stress intensities can be determined expeditiously using a small number of specimens. This procedure was developed to avoid or circumvent the effects of load interactions on fatigue crack growth, and was used to develop data on a mill annealed Ti-6Al-4V alloy plate. Experimental data suggest that the rates of fatigue crack growth among the various stress ratios may be correlated in terms of an effective stress intensity range at given values of K max. This procedure is not to be used, however, for determining the corrosion fatigue crack growth characteristics of alloys when nonsteady-state effects are significant.

78 FR 52841 - Airworthiness Directives; Lockheed Martin Corporation/Lockheed Martin Aeronautics Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-27

...-1011 series airplanes. AD 2005-15-01 required repetitive inspections to detect corrosion or fatigue... threshold required by the AD 2005-15-01. We are issuing this AD to prevent corrosion or fatigue cracking of... threshold required by AD 2005-15-01. We are issuing this AD to prevent corrosion or fatigue cracking of...

Grease Inhibits Stress-Corrosion Cracking In Bearing Race

NASA Technical Reports Server (NTRS)

Beatty, Robert F.; Mcvey, Scott E.

1991-01-01

Coating with suitable grease found to inhibit stress-corrosion cracking in bore of inner race of ball-bearing assembly operating in liquid oxygen. Protects bore and its corner radii from corrosion-initiating and -accelerating substances like moisture and contaminants, which enter during assembly. Operating life extended at low cost, and involves very little extra assembly time.

Effect of cloric acid concentration on corrosion behavior of Ni/Cr coated on carbon steel

NASA Astrophysics Data System (ADS)

Desiati, Resetiana Dwi; Sugiarti, Eni; Thosin, K. A. Zaini

2018-05-01

Corrosion is one of the causes of metal degradation. Carbon steel (Fe) is easy to corrode in the extreme environment. Coating on carbon steel is required to improve corrosion resistance owing to protection or hindrance to extreme environmental conditions. In this present work, carbon steel was coated by electroplating techniques for nickel and pack cementation for chrome. The corrosion rate test was performed by Weight Loss method on FeNiCr, FeNi, FeCr and uncoated Fe as comparator which was dyed in 37% HCl and 25% HCl which had previously been measured dimension and mass. The immersion test result of FeNiCr and FeNi specimen were better than FeCr and uncoated Fe in terms of increasing corrosion resistance. The corrosion rate for 56 hours in 37% HCl for FeNiCr was 1.592 mm/y and FeNi was 3.208 mm/y, FeCr only lasted within 32 hours with corrosion rate was 6.494 mm/y. Surface of the sample after the corrosion test there was pitting, crevice corrosion and alloy cracking caused by chloride. The higher the concentration of HCl the faster the corrosion rate.

Plasma surface tantalum alloying on titanium and its corrosion behavior in sulfuric acid and hydrochloric acid

NASA Astrophysics Data System (ADS)

Wei, D. B.; Chen, X. H.; Zhang, P. Z.; Ding, F.; Li, F. K.; Yao, Z. J.

2018-05-01

An anti-corrosion Ti-Ta alloy coating was prepared on pure titanium surface by double glow plasma surface alloying technology. Electrochemical corrosion test was applied to test the anti-corrosion property of Ti-Ta alloy layer. The microstructure and the phase composition of Ti-Ta alloy coating were detected before and after corrosion process by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The results showed that the Ta-Ti alloy layer has a thickness of about 13-15 μm, which is very dense without obvious defects such as pores or cracks. The alloy layer is composed mainly of β-Ta and α-Ti. The Ta alloy layer improves the anti-corrosion property of pure titanium. A denser and more durable TiO2 formed on the surface Ta-Ti alloy layer after immersing in strong corrosive media may account for the excellent corrosion resistant.

Stress-corrosion crack-growth study of titanium alloy Ti-6Al-4V exposed to freon PCA and nitrogen tetroxide MON-1

NASA Technical Reports Server (NTRS)

Bjorklund, R. A.

1983-01-01

An experimental fracture mechanics program was performed to determine the stress corrosion crack growth sensitivity of the propellant tank material, titanium alloy Ti-6Al-4V, for aerospace satellite applications involving long term exposure to Freon PCA and nitrogen tetroxide MON-1. Sustained load tests were made at a 49 C (120 F) constant temperature using thin gauge tensile test specimens containing semielliptical surface flaws. Test specimen types included parent metal, center of weld, and weld heat affected zone. It was concluded that Ti-6Al-4V alloy is not adversely affected in a stress environment when exposed to Freon PCA for 1000 hours followed by exposure to nitrogen tetroxide MON-1 for 2000 hours at stress levels up to 80% of the experimental critical plane strain stress intensity factor.

Northwest Manufacturing Initiative

DTIC Science & Technology

2012-03-27

crack growth and threshold stress corrosion cracking evaluation. Threshold stress corrosion cracking was done using the rising step load method with...Group Technology methods to establish manufacturing cells for production efficiency, to develop internal Lean Champions, and to implement rapid... different levels, advisory, core, etc. VI. Core steering committee composed of members that have a significant vested interest. Action Item: Draft

Failure investigations of failed valve plug SS410 steel due to cracking

NASA Astrophysics Data System (ADS)

Kalyankar, V. D.; Deshmukh, D. D.

2017-12-01

Premature and sudden in service failure of a valve plug due to crack formation, applied in power plant has been investigated. The plug was tempered and heat treated, the crack was originated at centre, developed along the axis and propagates radially towards outer surface of plug. The expected life of the component is 10-15 years while, the component had failed just after the installation that is, within 3 months of its service. No corrosion products were observed on the crack interface and on the failed surface; hence, causes of corrosion failure are neglected. This plug of level separator control valve, is welded to the stem by means of plasma-transferred arc welding and as there is no crack observed at the welding zone, the failure due to welding residual stresses are also neglected. The failed component discloses exposed surface of a crack interface that originated from centre and propagates radially. The micro-structural observation, hardness testing, and visual observation are carried out of the specimen prepared from the failed section and base portion. The microstructure from the cracked interface showed severe carbide formation along the grain boundaries. From the microstructural analysis of the failed sample, it is observed that there is a formation of acicular carbides along the grain boundaries due to improper tempering heat treatment.

Effect of water vapor on fatigue crack growth in 7475-T651 aluminum alloy plate. [for aerospace applications

NASA Technical Reports Server (NTRS)

Dicus, D. L.

1984-01-01

The effects of water vapor on fatigue crack growth in 7475-T651 aluminum alloy plate at frequencies of 1 Hz and 10 Hz were investigated. Twenty-five mm thick compact specimens were subjected to constant amplitude fatigue testing at a load ratio of 0.2. Fatigue crack growth rates were calculated from effective crack lengths determined using a compliance method. Tests were conducted in hard vacuum and at water vapor partial pressures ranging from 94 Pa to 3.8 kPa. Fatigue crack growth rates were frequency insensitive under all environment conditions tested. For constant stress intensity factor ranges crack growth rate transitions occurred at low and high water vapor pressures. Crack growth rates at intermediate pressures were relatively constant and showed reasonable agreement with published data for two Al-Cu-Mg alloys. The existence of two crack growth rate transitions suggests either a change in rate controlling kinetics or a change in corrosion fatigue mechanism as a function of water vapor pressure. Reduced residual deformation and transverse cracking specimens tested in water vapor versus vacuum may be evidence of embrittlement within the plastic zone due to environmental interaction.

The effect of water vapor on fatigue crack Growth in 7475-t651 aluminum alloy plate. [for aerospace applications

NASA Technical Reports Server (NTRS)

Dicus, D. L.

1982-01-01

The effects of water vapor on fatigue crack growth in 7475-T651 aluminum alloy plate at frequencies of 1 Hz and 10 Hz were investigated. Twenty-five mm thick compact specimens were subjected to constant amplitude fatigue testing at a load ratio of 0.2. Fatigue crack growth rates were calculated from effective crack lengths determined using a compliance method. Tests were conducted in hard vacuum and at water vapor partial pressures ranging from 94 Pa to 3.8 kPa. Fatigue crack growth rates were frequency insensitive under all environment conditions tested. For constant stress intensity factor ranges crack growth rate transitions occurred at low and high water vapor pressures. Crack growth rates at intermediate pressures were relatively constant and showed reasonable agreement with published data for two Al-Cu-Mg alloys. The existence of two crack growth rate transitions suggests either a change in rate controlling kinetics or a change in corrosion fatigue mechanism as a function of water vapor pressure. Reduced residual deformation and transverse cracking specimens tested in water vapor versus vacuum may be evidence of embrittlement within the plastic zone due to environmental interaction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brickstad, B.; Bergman, M.

A computerized procedure has been developed that predicts the growth of an initial circumferential surface crack through a pipe and further on to failure. The crack growth mechanism can either be fatigue or stress corrosion. Consideration is taken to complex crack shapes and for the through-wall cracks, crack opening areas and leak rates are also calculated. The procedure is based on a large number of three-dimensional finite element calculations of cracked pipes. The results from these calculations are stored in a database from which the PC-program, denoted LBBPIPE, reads all necessary information. In this paper, a sensitivity analysis is presentedmore » for cracked pipes subjected to both stress corrosion and vibration fatigue.« less

Role of pH on the stress corrosion cracking of titanium alloys

NASA Technical Reports Server (NTRS)

Khokhar, M. I.; Beck, F. H.; Fontana, M. G.

1973-01-01

Stress corrosion cracking (SCC) experiments were conducted on Ti-8-1-1 wire specimens in hydrochloric and sulfuric acids of variable pH in order to determine the effect of pH on the susceptibility to cracking. The alloy exhibited increasing susceptibility with decreasing pH. By varying the applied potential, it was observed that susceptibility zones exist both in the cathodic and the anodic ranges. In the cathodic range, susceptibility also increased with decreasing applied potential. Corrosion potential-time data in hydrochloric acid (pH 1.7) and sulfuric acid (pH 1.7) indicate that chloride ions lower the corrosion potential of the specimen which, in turn, increases the susceptibility.

Hot Corrosion of Inconel 625 Overlay Weld Cladding in Smelting Off-Gas Environment

NASA Astrophysics Data System (ADS)

Mohammadi Zahrani, E.; Alfantazi, A. M.

2013-10-01

Degradation mechanisms and hot corrosion behavior of weld overlay alloy 625 were studied. Phase structure, morphology, thermal behavior, and chemical composition of deposited salt mixture on the weld overlay were characterized utilizing XRD, SEM/EDX, DTA, and ICP/OES, respectively. Dilution level of Fe in the weldment, dendritic structure, and degradation mechanisms of the weld were investigated. A molten phase formed on the weld layer at the operating temperature range of the boiler, which led to the hot corrosion attack in the water wall and the ultimate failure. Open circuit potential and weight-loss measurements and potentiodynamic polarization were carried out to study the hot corrosion behavior of the weld in the simulated molten salt medium at 873 K, 973 K, and 1073 K (600 °C, 700 °C, and 800 °C). Internal oxidation and sulfidation plus pitting corrosion were identified as the main hot corrosion mechanisms in the weld and boiler tubes. The presence of a significant amount of Fe made the dendritic structure of the weld susceptible to preferential corrosion. Preferentially corroded (Mo, Nb)-depleted dendrite cores acted as potential sites for crack initiation from the surface layer. The penetration of the molten phase into the cracks accelerated the cracks' propagation mainly through the dendrite cores and further crack branching/widening.

Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Formed Domes

NASA Technical Reports Server (NTRS)

Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

2010-01-01

Simulated service testing (SST) development was required to help qualify a new 2195 aluminum lithium (Al-Li) alloy spin forming dome fabrication process for the National Aeronautics and Space Administration (NASA) Exploration Development Technology Program. The application for the technology is to produce high strength low weight tank components for NASA s next generation launch vehicles. Since plate material is not currently manufactured large enough to fabricate these domes, two plates are joined by means of friction stir welding. The plates are then pre-contour machined to near final thicknesses allowing for a thicker weld land and anticipating the level of stretch induced by the spin forming process. The welded plates are then placed in a spin forming tool and hot stretched using a trace method producing incremental contours. Finally the dome receives a room temperature contour stretch to final dimensions, heat treatment, quenching, and artificial aging to emulate a T-8 condition of temper. Stress corrosion cracking (SCC) tests were also performed by alternate immersion in a sodium chloride (NaCl) solution using the typical double beam assembly and with 4-point loaded specimens and use of bent-beam stress-corrosion test specimens under alternate immersion conditions. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K(sub ISCC)) which to our knowledge has not been determined previously for Al-Li 2195 alloy. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication

Avoidance of stress corrosion susceptibility in high strength aluminum alloys by control of grain boundary and matrix microstructure

NASA Technical Reports Server (NTRS)

Adler, P.; Deiasi, R.

1974-01-01

The relation of microstructure to the mechanical strength and stress corrosion resistance of highest strength and overaged tempers of BAR and 7050 aluminum alloys was investigated. Comparison is made with previously studied 7075 aluminum alloy. Optical microscopy, transmission electron microscopy, and differential scanning calorimetry were used to characterize the grain morphology, matrix microstructure, and grain boundary microstructure of these tempers. Grain boundary interparticle spacing was significant to stress corrosion crack propagation for all three alloys; increasing interparticle spacing led to increased resistance to crack propagation. In addition, the fire grain size in Bar and 7050 appears to enhance crack propagation. The highest strength temper of 7050 has a comparatively high resistance to crack initiation. Overall stress corrosion behavior is dependent on environment pH, and evaluation over a range of pH is recommended.

Analysis on the stress corrosion crack inception based on pit shape and size of the FV520B tensile specimen

NASA Astrophysics Data System (ADS)

Xiang, Longhao; Pan, Juyi; Chen, Songying

2018-06-01

The influence of pit shape and size on local stress concentration in the tensile specimen and the stress corrosion cracks inception was studied by employing the element remove technique. The maximum stress located in the bottom of pit on FV520B tensile specimen. The location of maximum strain was near the mouth of the pit or the shoulder and plastic strain existed in this region. Stress concentration factor and plastic deformation on four different geometrical shape pits of hemisphere, semi-ellipsoid, bullet and butterfly were numerically investigated, respectively. The simulation results showed that butterfly pit got the biggest stress concentration factor. The plastic strain rate during pit growth was in the sensitivity range of stress corrosion cracks inception, indicating that stress corrosion cracks were more likely to nucleate near the pit tip or the shoulder.

Evaluation of Stress Corrosion Resistance Properties of 15CrMoR(H) in H2S Environment

NASA Astrophysics Data System (ADS)

Zhang, Yiliang; Wang, Jing; Wu, Mingyao; Li, Shurui; Liu, Wenbin

To evaluate the hydrogen resistant properties of the 15CrMoR(H) with new smelting process, according to NACE and National Standards, three tests including NACE standard tensile test, NACE standard bent-beam test and hydrogen induced cracking test are executed in saturated hydrogen sulfide(H2S) environment. Stress-life mathematical model of this material is given by analyzing and fitting the results of tensile test. Test results show that the threshold sth of tensile test is 0.7R eL(252MPa); the threshold nominal stress SC of bent-beam is higher than 4.5 R eL (1620MPa); for HIC test, the crack length rate CLR is 4.40%, the crack thickness rate CTR is 0.87% and the crack sensitive rate CSR is 0.04%. Compare with EFC standard, the safety margin of HIC test is 3.4, 3.4 and 37.5 times respectively. All the experimental results show that the new 15CrMoR(H) material has excellent H2S environmental cracking resistance properties.

Remote detection of stress corrosion cracking: Surface composition and crack detection

NASA Astrophysics Data System (ADS)

Lissenden, Cliff J.; Jovanovic, Igor; Motta, Arthur T.; Xiao, Xuan; Le Berre, Samuel; Fobar, David; Cho, Hwanjeong; Choi, Sungho

2018-04-01

Chloride induced stress corrosion cracking (SCC) of austenitic stainless steel is a potential issue in long term dry storage of spent nuclear fuel canisters. In order for SCC to occur there must be a corrosive environment, a susceptible material, and a driving force. Because it is likely that the material in the heat affected zone (HAZ) of welded stainless steel structures has been sensitized as a result of chromium depletion at the grain boundaries and a thermal residual stress driving force is likely present if solution annealing is not performed, two issues are critical. Is the environment corrosive, i.e., are chlorides present in solution on the surface? And then, are there cracks that could propagate? Remote detection of chlorides on the surface can be accomplished by laser induced breakdown spectroscopy (LIBS), while cracks can be detected by shear horizontal guided waves generated by electromagnetic acoustic transducers (EMATs). Both are noncontact methods that are amenable to robotic delivery systems and harsh environments. The sensitivity to chlorine on stainless steel of a LIBS system that employs optical fiber for pulse delivery is demonstrated. Likewise, the ability of the EMAT system to detect cracks of a prescribed size and orientation is shown. These results show the potential for remote detection of Cl and cracks in dry storage spent fuel canisters.

75 FR 61977 - Airworthiness Directives; The Boeing Company Model 747-100, 747-200B, and 747-200F Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-07

... fatigue-related skin cracks and corrosion of the skin panel lap joints in the fuselage upper lobe, and... of corrosion, and related investigative and corrective actions. This AD reduces the maximum interval... and correct fatigue cracking and corrosion in the fuselage upper lobe skin lap joints, which could...

Quantification of the Service Life Extension and Environmental Benefit of Chloride Exposed Self-Healing Concrete

PubMed Central

Van Belleghem, Bjorn; Van den Heede, Philip; Van Tittelboom, Kim; De Belie, Nele

2016-01-01

Formation of cracks impairs the durability of concrete elements. Corrosion inducing substances, such as chlorides, can enter the matrix through these cracks and cause steel reinforcement corrosion and concrete degradation. Self-repair of concrete cracks is an innovative technique which has been studied extensively during the past decade and which may help to increase the sustainability of concrete. However, the experiments conducted until now did not allow for an assessment of the service life extension possible with self-healing concrete in comparison with traditional (cracked) concrete. In this research, a service life prediction of self-healing concrete was done based on input from chloride diffusion tests. Self-healing of cracks with encapsulated polyurethane precursor formed a partial barrier against immediate ingress of chlorides through the cracks. Application of self-healing concrete was able to reduce the chloride concentration in a cracked zone by 75% or more. As a result, service life of steel reinforced self-healing concrete slabs in marine environments could amount to 60–94 years as opposed to only seven years for ordinary (cracked) concrete. Subsequent life cycle assessment calculations indicated important environmental benefits (56%–75%) for the ten CML-IA (Center of Environmental Science of Leiden University–Impact Assessment) baseline impact indicators which are mainly induced by the achievable service life extension. PMID:28772363

Materials for Consideration in Standardized Canister Design Activities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryan, Charles R.; Ilgen, Anastasia Gennadyevna; Enos, David George

2014-10-01

This document identifies materials and material mitigation processes that might be used in new designs for standardized canisters for storage, transportation, and disposal of spent nuclear fuel. It also addresses potential corrosion issues with existing dual-purpose canisters (DPCs) that could be addressed in new canister designs. The major potential corrosion risk during storage is stress corrosion cracking of the weld regions on the 304 SS/316 SS canister shell due to deliquescence of chloride salts on the surface. Two approaches are proposed to alleviate this potential risk. First, the existing canister materials (304 and 316 SS) could be used, but themore » welds mitigated to relieve residual stresses and/or sensitization. Alternatively, more corrosion-resistant steels such as super-austenitic or duplex stainless steels, could be used. Experimental testing is needed to verify that these alternatives would successfully reduce the risk of stress corrosion cracking during fuel storage. For disposal in a geologic repository, the canister will be enclosed in a corrosion-resistant or corrosion-allowance overpack that will provide barrier capability and mechanical strength. The canister shell will no longer have a barrier function and its containment integrity can be ignored. The basket and neutron absorbers within the canister have the important role of limiting the possibility of post-closure criticality. The time period for corrosion is much longer in the post-closure period, and one major unanswered question is whether the basket materials will corrode slowly enough to maintain structural integrity for at least 10,000 years. Whereas there is extensive literature on stainless steels, this evaluation recommends testing of 304 and 316 SS, and more corrosion-resistant steels such as super-austenitic, duplex, and super-duplex stainless steels, at repository-relevant physical and chemical conditions. Both general and localized corrosion testing methods would be used to establish corrosion rates and component lifetimes. Finally, it is unlikely that the aluminum-based neutron absorber materials that are commonly used in existing DPCs would survive for 10,000 years in disposal environments, because the aluminum will act as a sacrificial anode for the steel. We recommend additional testing of borated and Gd-bearing stainless steels, to establish general and localized corrosion resistance in repository-relevant environmental conditions.« less

Identification of corrosion and damage mechanisms by using scanning electron microscopy and energy-dispersive X-ray microanalysis: contribution to failure analysis case histories

NASA Astrophysics Data System (ADS)

Pantazopoulos, G.; Vazdirvanidis, A.

2014-03-01

Emphasis is placed on the evaluation of corrosion failures of copper and machineable brass alloys during service. Typical corrosion failures of the presented case histories mainly focussed on stress corrosion cracking and dezincification that acted as the major degradation mechanisms in components used in piping and water supply systems. SEM assessment, coupled with EDS spectroscopy, revealed the main cracking modes together with the root-source(s) that are responsible for the damage initiation and evolution. In addition, fracture surface observations contributed to the identification of the incurred fracture mechanisms and potential environmental issues that stimulated crack initiation and propagation. Very frequently, the detection of chlorides among the corrosion products served as a suggestive evidence of the influence of working environment on passive layer destabilisation and metal dissolution.

Environmental Effects on the Incubation Time Characteristics in Stress-Corrosion Cracking

DTIC Science & Technology

2011-04-01

Corrosion Experimental Data for Specimen SL51 143 Table B2. Stress Corrosion Experimental Data for Specimen SL76 (3.5% NaCI, K , =6.8M/Wm) 144 Table B3...of action of the external load; - 143 - K =applied stress intensity factor; da/dt=crack growth rate. Table B2. Stress Corrosion Experimental Data for...Submitted to Dr. Asuri K . Vasudevan Scientific Officer Office of Naval Research, Code-332 875 North Randolph Street, Suite 1425, Room- 629

Friction Stir Welding of Al Alloy 2219-T8: Part II-Mechanical and Corrosion

NASA Astrophysics Data System (ADS)

Kang, Ju; Feng, Zhi-Cao; Li, Ji-Chao; Frankel, G. S.; Wang, Guo-Qing; Wu, Ai-Ping

2016-09-01

In Part I of this series, abnormal agglomerations of θ particles with size of about 100 to 1000 µm were observed in friction stir welded AA2219-T8 joints. In this work, the effects of these agglomerated θ particles on the mechanical and corrosion properties of the joints are studied. Tensile testing with in situ SEM imaging was utilized to monitor crack initiation and propagation in base metal and weld nugget zone (WNZ) samples. These tests showed that cracks initiated in the θ particles and at the θ/matrix interfaces, but not in the matrix. The WNZ samples containing abnormal agglomerated θ particles had a similar ultimate tensile stress but 3 pct less elongation than other WNZ samples with only normal θ particles. Measurements using the microcell technique indicated that the agglomerated θ particles acted as a cathode causing the dissolution of adjacent matrix. The abnormal θ particle agglomerations led to more severe localized attack due to the large cathode/anode ratio. Al preferential dissolution occurred in the abnormal θ particle agglomerations, which was different from the corrosion behavior of normal size θ particles.

3013 DE INNER CONTAINER CLOSURE WELD CORROSION EVALUATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mickalonis, J.

Destructive evaluation (DE) of 3013 containers is one part of the U. S. Department of Energy Integrated Surveillance Program. During standard DE of 3013 containers, visual examinations for pitting and stress corrosion cracking (SCC) are performed on the accessible surfaces of the outer, inner, and convenience containers, which make up the 3013 container. As a result of 3013 DE additional analysis, the area near the inner container closure weld has been identified as being a region of increased corrosion susceptibility, which may provide a pathway for corrosive gases to the outer container. This area has a higher residual stress, anmore » altered microstructure, and less corrosion resistant weld oxides as a result of the welding process as well as a lower temperature than other areas of the container, which may increase the absorption of moisture on the surface. The deposition of moisture in this stressed region could lead to pitting and stress corrosion cracking. During FY2013, the inner container closure weld area was more closely evaluated on several archived samples from DE containers. These containers included FY09 DE2, FY12 DE4, FY12 DE6 and FY12 DE7 and the Hanford High Moisture Container. The additional examinations included visual observations with a stereomicroscope, scanning electron microscopy along with energy dispersive spectroscopy for chemical analysis, and serial metallography of the sidewall and lid that are part of the inner container closure weld region. Pitting was observed in all the samples taken from the closure weld regions of the examined inner containers. This pitting was generally less 20 μm with most less than 5m. These pits were similar in depth to those observed in the vapor exposed surfaces of teardrops in the shelf life corrosion testing. Cracking was not observed on either the vapor-exposed surfaces of the teardrop coupons or the inner container closure weld region. Further testing is necessary to determine if the conditions in the welded inner container could support SCC during the 50 year life time for the 3013 container.« less

Corrosion and Potentiostatic Polarization of an Al-Cu-Li Alloy under Tensile Stress

NASA Astrophysics Data System (ADS)

Li, Jin-feng; Zheng, Zi-qiao

The stress corrosion cracking (SCC) of an Al-3.8Cu-1.5Li-0.5Zn-0.5Mg-0.3Mn alloy in 3.5% NaCl solution was studied through using slow strain rate tension(SSRT). The potentiodynamic polarization and anodic potentiostastic polarization of the stressed and stress free alloy with T6 temper were investigated. The tensile stress decreased the break down potential. The alloy was sensitive to intergranular SCC (IGSCC), due to the continuous distribution of anodic phase of T2(Al6CuLi3) along the grain boundary. During the potentiostastic polarization, the current-time curve of the stressed alloy displayed a repeated transient feature that the current increased suddenly followed by a slower recovery, and corrosion crack appeared along the grain boundary. While the stress free alloy did not show this current feature and corrosion crack along the grain boundary. The repeated current transient was associated with the crack tip propagation and crack wall passivation. This feature may be used to analyze the SCC process.

Evaluation of Stress Corrosion Cracking Susceptibility Using Fracture Mechanics Techniques, Part 1. [environmental tests of aluminum alloys, stainless steels, and titanium alloys

NASA Technical Reports Server (NTRS)

Sprowls, D. O.; Shumaker, M. B.; Walsh, J. D.; Coursen, J. W.

1973-01-01

Stress corrosion cracking (SSC) tests were performed on 13 aluminum alloys, 13 precipitation hardening stainless steels, and two titanium 6Al-4V alloy forgings to compare fracture mechanics techniques with the conventional smooth specimen procedures. Commercially fabricated plate and rolled or forged bars 2 to 2.5-in. thick were tested. Exposures were conducted outdoors in a seacoast atmosphere and in an inland industrial atmosphere to relate the accelerated tests with service type environments. With the fracture mechanics technique tests were made chiefly on bolt loaded fatigue precracked compact tension specimens of the type used for plane-strain fracture toughness tests. Additional tests of the aluminum alloy were performed on ring loaded compact tension specimens and on bolt loaded double cantilever beams. For the smooth specimen procedure 0.125-in. dia. tensile specimens were loaded axially in constant deformation type frames. For both aluminum and steel alloys comparative SCC growth rates obtained from tests of precracked specimens provide an additional useful characterization of the SCC behavior of an alloy.

Influence of Stress Corrosion Crack Morphology on Ultrasonic Examination Performances

NASA Astrophysics Data System (ADS)

Dupond, O.; Duwig, V.; Fouquet, T.

2009-03-01

Stress Corrosion Cracking represents a potential damage for several components in PWR. For this reason, NDE of stress corrosion cracks corresponds to an important stake for Electricité de France (EDF) both for availability and for safety of plants. This paper is dedicated to the ultrasonic examination of SCC crack defects. The study mixes an experimental approach conducted on artificial flaws—meant to represent the characteristic morphologic features often encountered on SCC cracks—and a 2D finite element modelling with the code ATHENA 2D developed by EDF. Results indicate that ATHENA reproduces correctly the interaction of the beam on the complex defect. Indeed specific ultrasonic responses resulting from the defect morphology have been observed experimentally and reproduced with the modelling.

The effect of alloy composition on the mechanism of stress corrosion cracking of titanium alloys in aqueous environments

NASA Technical Reports Server (NTRS)

Boyd, J. D.; Williams, D. N.; Wood, R. A.; Jaffee, R. I.

1972-01-01

The effects of alloy composition on the aqueous stress corrosion of titanium alloys were studied with emphasis on determining the interrelations among composition, phase structure, and deformation and fracture properties of the alpha phase in alpha-beta alloys. Accomplishments summarized include the effects of alloy composition on susceptibility, and metallurgical mechanisms of stress-corrosion cracking.

Report on Status of Shipment of High Fluence Austenitic Steel Samples for Characterization and Stress Corrosion Crack Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Scarlett R.; Leonard, Keith J.

The goal of the Mechanisms of Irradiation Assisted Stress Corrosion Cracking (IASCC) task in the LWRS Program is to conduct experimental research into understanding how multiple variables influence the crack initiation and crack growth in materials subjected to stress under corrosive conditions. This includes understanding the influences of alloy composition, radiation condition, water chemistry and metallurgical starting condition (i.e., previous cold work or heat treatments and the resulting microstructure) has on the behavior of materials. Testing involves crack initiation and growth testing on irradiated specimens of single-variable alloys in simulated Light Water Reactor (LWR) environments, tensile testing, hardness testing, microstructuralmore » and microchemical analysis, and detailed efforts to characterize localized deformation. Combined, these single-variable experiments will provide mechanistic understanding that can be used to identify key operational variables to mitigate or control IASCC, optimize inspection and maintenance schedules to the most susceptible materials/locations, and, in the long-term, design IASCC-resistant materials. In support of this research, efforts are currently underway to arrange shipment of “free” high fluence austenitic alloys available through Électricité de France (EDF) for post irradiation testing at the Oak Ridge National Laboratory (ORNL) and IASCC testing at the University of Michigan. These high fluence materials range in damage values from 45 to 125 displacements per atom (dpa). The samples identified for transport to the United States, which include nine, no-cost, 304, 308 and 316 tensile bars, were relocated from the Research Institute of Atomic Reactors (RIAR) in Dimitrovgrad, Ulyanovsk Oblast, Russia, and received at the Halden Reactor in Halden, Norway, on August 23, 2016. ORNL has been notified that a significant amount of work is required to prepare the samples for further shipment to Oak Ridge, Tennessee. The preliminary work for sample shipment between Halden and Oak Ridge includes fabrication of an inner cask sample container, decontamination and preparation of a Type A container, preparation of new activity calculations, all necessary paperwork, and handling. ORNL will continue to work to track progress of sample preparation and shipment status, and to work toward an agreement that covers material shipping costs between the Halden Reactor and the Oak Ridge National Laboratory.« less

Fatigue 󈨛. Volume 3,

DTIC Science & Technology

1987-06-01

Corrosion and Cathodic Protection 1169 on Crack Growth in Offshore Platform Steels in Sea Water - EINAR BARDAL The Influence of Crack Conditions on...PROTECTION ON CRACK GROWTH IN OFFSHORE PLATFORM STEELS IN SEA WATER: EINAR BARDAL* Corrosion fatigue of steel for offshore platforms has been studied at...surfaces (6). When results from experiments with natural sea water are compared with corresponding results obtained in synthetic sea water, no significant

77 FR 26663 - Airworthiness Directives; The Boeing Company Model 767-200, -300, -300F, and -400ER Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-07

... removing corrosion from fail-safe straps. We have received Boeing Service Bulletin 767-53A0100, Revision 3.... That AD currently requires inspections to detect cracking or corrosion of the fail-safe straps between... cracks in 51 fail-safe straps on 41 airplanes; we have also received a report of a crack found in the ``T...

Mechanical behavior of precipitation hardenable steels exposed to highly corrosive environment

NASA Technical Reports Server (NTRS)

Rosa, Ferdinand

1994-01-01

Unexpected occurrences of failures, due to stress corrosion cracking (SCC) of structural components, indicate a need for improved characterization of materials and more advanced analytical procedures for reliably predicting structures performance. Accordingly, the purpose of this study was to determine the stress corrosion susceptibility of 15 - 5 PH steel over a wide range of applied strain rates in a highly corrosive environment. The selected environment for this investigation was a 3.5 percent NaCl aqueous solution. The material selected for the study was 15 - 5 PH steel in the H 900 condition. The Slow Strain Rate technique was used to test the metallic specimens.

Development of Eddy Current Technique for the Detection of Stress Corrosion Cracking in Space Shuttle Primary Reaction Control Thrusters

NASA Technical Reports Server (NTRS)

Wincheski, Buzz; Simpson, John; Koshti, Ajay

2006-01-01

A recent identification of stress corrosion cracking in the Space Shuttle Primary Reaction Control System (PRCS) thrusters triggered an extensive nondestructive evaluation effort to develop techniques capable of identifying such damage on installed shuttle hardware. As a part of this effort, specially designed eddy current probes inserted into the acoustic cavity were explored for the detection of such flaws and for evaluation of the remaining material between the crack tip and acoustic cavity. The technique utilizes two orthogonal eddy current probes which are scanned under stepper motor control in the acoustic cavity to identify cracks hidden with as much as 0.060 remaining wall thickness to the cavity. As crack growth rates in this area have been determined to be very slow, such an inspection provides a large safety margin for continued operation of the critical shuttle hardware. Testing has been performed on thruster components with both actual and fabricated defects. This paper will review the design and performance of the developed eddy current inspection system. Detection of flaws as a function of remaining wall thickness will be presented along with the proposed system configuration for depot level or on-vehicle inspection capabilities.

A Crack Growth Evaluation Method for Interacting Multiple Cracks

NASA Astrophysics Data System (ADS)

Kamaya, Masayuki

When stress corrosion cracking or corrosion fatigue occurs, multiple cracks are frequently initiated in the same area. According to section XI of the ASME Boiler and Pressure Vessel Code, multiple cracks are considered as a single combined crack in crack growth analysis, if the specified conditions are satisfied. In crack growth processes, however, no prescription for the interference between multiple cracks is given in this code. The JSME Post-Construction Code, issued in May 2000, prescribes the conditions of crack coalescence in the crack growth process. This study aimed to extend this prescription to more general cases. A simulation model was applied, to simulate the crack growth process, taking into account the interference between two cracks. This model made it possible to analyze multiple crack growth behaviors for many cases (e. g. different relative position and length) that could not be studied by experiment only. Based on these analyses, a new crack growth analysis method was suggested for taking into account the interference between multiple cracks.

Corrosion fatigue crack growth behavior of titanium alloys in aqueous solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shipilov, S.A.

1998-01-01

The corrosion fatigue crack growth (FCG) behavior, the effect of applied potential on corrosion FCG rates, and the fracture surfaces of VT20 (near-{alpha}) and TS6 (near-{beta}) titanium alloys were studied. Environments were aqueous solutions of sodium chloride (NaCl), sodium hydroxide (NaOH), potassium hydroxide (KOH), ferric chloride (FeCl{sub 3}), and chromic acid (H{sub 2}CrO{sub 4}) with and without NaCl. Depending upon solution composition, corrosion FCG rates were found to be higher or lower than those in air. Cathodic polarization retarded the corrosion FCG, while anodic polarization accelerated insignificantly or almost did not influence it in most of the solutions investigated. However,more » cathodic polarization accelerated corrosion FCG in 0.6 M FeCl{sub 3} and 0.5 M to 2 M H{sub 2}CrO{sub 4} + 0.01 M to 0.1 M NaCl solutions by a dozen times when the maximum stress intensity (K{sub max}) exceeded certain critical values. When K{sub max} was lower than the critical values, the same cathodic polarization (with all other /conditions being equal) retarded corrosion FCG. Results suggested the accelerated crack growth at cathodic potentials resulted from hydrogen-induced cracking (HIC). Therefore, critical values of K{sub max}, as well as the stress intensity range ({Delta}K) were regarded as corresponding to the beginning of corrosion FCG according to a HIC mechanism and designated as K{sub HIC} and {Delta}K{sub HIC}.« less

FINAL ANALYTICAL RESULTS FROM THE EXAMINATION OF CORROSION ON SECTIONS OF CORROSION PROBE REMOVED FROM TANK 241-AN-107 ON 08/10/2006

DOE Office of Scientific and Technical Information (OSTI.GOV)

DUNCAN JB; COOKE GA

2007-03-22

Tank Farms Operations removed an electrochemical noise probe from Tank 241-AN-107. In the field, the probe was cut into four sections, wrapped, and placed in a 55-gallon drum, This drum was delivered to the 222-S Laboratory. The 222 S Laboratory unpackaged the sections of the AN-107 electrochemical noise probe and examined the material for evidence of corrosion. Each of the four sections contained three C-ring and three bullet specimens. The specimens were examined for pitting corrosion, crevice corrosion, and stress corrosion cracking. No evidence of stress corrosion cracking was found in the stressed C-ring specimens. Minor pitting was evident onmore » some surfaces. Crevice corrosion was the dominant type of corrosion observed.« less

Kinetic studies of the stress corrosion cracking of D6AC steel

NASA Technical Reports Server (NTRS)

Noronha, P. J.

1975-01-01

The effect of load interactions on the crack growth velocity of D6AC steel under stress corrosion cracking conditions was determined. The environment was a 3.5 percent salt solution. The modified-wedge opening load specimens were fatigue precracked and subjected to a deadweight loading in creep machines. The effects of load shedding on incubation times and crack growth rates were measured using high-sensitivity compliance measurement techniques. Load shedding results in an incubation time, the length of which depends on the amount of load shed and the baseline stress intensity. The sequence of unloading the specimen also controls the subsequent incubation period. The incubation period is shorter when load shedding passes through zero load than when it does not if the specimen initially had the same baseline stress intensity. The crack growth rates following the incubation period are also different from the steady-state crack growth rate at the operating stress intensity. These data show that the susceptibility of this alloy system to stress corrosion cracking depends on the plane-strain fracture toughness and on the yield strength of the material.

Analysis of stress corrosion cracking in alloy 718 following commercial reactor exposure

DOE PAGES

Leonard, Keith J.; Gussev, Maxim N.; Stevens, Jacqueline N.; ...

2015-08-24

Alloy 718 is generally considered a highly corrosion-resistant material but can still be susceptible to stress corrosion cracking (SCC). The combination of factors leading to SCC susceptibility in the alloy is not always clear enough. In this paper, alloy 718 leaf spring (LS) materials that suffered stress corrosion damage during two 24-month cycles in pressurized water reactor service, operated to >45 MWd/mtU burn-up, was investigated. Compared to archival samples fabricated through the same processing conditions, little microstructural and property changes occurred in the material with in-service irradiation, contrary to high dose rate laboratory-based experiments reported in literature. Though the lackmore » of delta phase formation along grain boundaries would suggest a more SCC resistant microstructure, grain boundary cracking in the material was extensive. Crack propagation routes were explored through focused ion beam milling of specimens near the crack tip for transmission electron microscopy as well as in polished plan view and cross-sectional samples for electron backscatter diffraction analysis. It has been shown in this study that cracks propagated mainly along random high-angle grain boundaries, with the material around cracks displaying a high local density of dislocations. The slip lines were produced through the local deformation of the leaf spring material above their yield strength. Also, the cause for local SCC appears to be related to oxidation of both slip lines and grain boundaries, which under the high in-service stresses resulted in crack development in the material.« less

Monitoring Concrete Deterioration Due to Reinforcement Corrosion by Integrating Acoustic Emission and FBG Strain Measurements

PubMed Central

Li, Weijie; Xu, Changhang; Ho, Siu Chun Michael; Wang, Bo; Song, Gangbing

2017-01-01

Corrosion of concrete reinforcement members has been recognized as a predominant structural deterioration mechanism for steel reinforced concrete structures. Many corrosion detection techniques have been developed for reinforced concrete structures, but a dependable one is more than desired. Acoustic emission technique and fiber optic sensing have emerged as new tools in the field of structural health monitoring. In this paper, we present the results of an experimental investigation on corrosion monitoring of a steel reinforced mortar block through combined acoustic emission and fiber Bragg grating strain measurement. Constant current was applied to the mortar block in order to induce accelerated corrosion. The monitoring process has two aspects: corrosion initiation and crack propagation. Propagation of cracks can be captured through corresponding acoustic emission whereas the mortar expansion due to the generation of corrosion products will be monitored by fiber Bragg grating strain sensors. The results demonstrate that the acoustic emission sources comes from three different types, namely, evolution of hydrogen bubbles, generation of corrosion products and crack propagation. Their corresponding properties are also discussed. The results also show a good correlation between acoustic emission activity and expansive strain measured on the specimen surface. PMID:28327510

Monitoring Concrete Deterioration Due to Reinforcement Corrosion by Integrating Acoustic Emission and FBG Strain Measurements.

PubMed

Li, Weijie; Xu, Changhang; Ho, Siu Chun Michael; Wang, Bo; Song, Gangbing

2017-03-22

Corrosion of concrete reinforcement members has been recognized as a predominant structural deterioration mechanism for steel reinforced concrete structures. Many corrosion detection techniques have been developed for reinforced concrete structures, but a dependable one is more than desired. Acoustic emission technique and fiber optic sensing have emerged as new tools in the field of structural health monitoring. In this paper, we present the results of an experimental investigation on corrosion monitoring of a steel reinforced mortar block through combined acoustic emission and fiber Bragg grating strain measurement. Constant current was applied to the mortar block in order to induce accelerated corrosion. The monitoring process has two aspects: corrosion initiation and crack propagation. Propagation of cracks can be captured through corresponding acoustic emission whereas the mortar expansion due to the generation of corrosion products will be monitored by fiber Bragg grating strain sensors. The results demonstrate that the acoustic emission sources comes from three different types, namely, evolution of hydrogen bubbles, generation of corrosion products and crack propagation. Their corresponding properties are also discussed. The results also show a good correlation between acoustic emission activity and expansive strain measured on the specimen surface.

Modeling time-dependent corrosion fatigue crack propagation in 7000 series aluminum alloys

NASA Technical Reports Server (NTRS)

Mason, Mark E.; Gangloff, Richard P.

1994-01-01

Stress corrosion cracking and corrosion fatigue experiments were conducted with the susceptible S-L orientation of AA7075-T651, immersed in acidified and inhibited NaCl solution, to provide a basis for incorporating environmental effects into fatigue crack propagation life prediction codes such as NASA FLAGRO. This environment enhances da/dN by five to ten-fold compared to fatigue in moist air. Time-based crack growth rates from quasi-static load experiments are an order of magnitude too small for accurate linear superposition prediction of da/dN for loading frequencies above 0.001 Hz. Alternate methods of establishing da/dt, based on rising-load or ripple-load-enhanced crack tip strain rate, do not increase da/dt and do not improve linear superposition. Corrosion fatigue is characterized by two regimes of frequency dependence; da/dN is proportional to f(exp -1) below 0.001 Hz and to F(exp 0) to F(exp -0.1) for higher frequencies. Da/dN increases mildly both with increasing hold-time at K(sub max) and with increasing rise-time for a range of loading waveforms. The mild time-dependence is due to cycle-time-dependent corrosion fatigue growth. This behavior is identical for S-L nd L-T crack orientations. The frequency response of environmental fatigue in several 7000 series alloys is variable and depends on undefined compositional or microstructural variables. Speculative explanations are based on the effect of Mg on occluded crack chemistry and embritting hydrogen uptake, or on variable hydrogen diffusion in the crack tip process zone. Cracking in the 7075/NaCl system is adequately described for life prediction by linear superposition for prolonged load-cycle periods, and by a time-dependent upper bound relationship between da/dN and delta K for moderate loading times.

Corrosion of cordierite ceramics by sodium sulphate at 1000 C

NASA Technical Reports Server (NTRS)

Bianco, Robert; Jacobson, Nathan

1989-01-01

The corrosion of a sintered cordierite (2MgO-2Al2O3-5SiO2) ceramic by sodium sulphate (Na2SO4) was investigated at 1000 C. Laboratory tests with thin films of Na2SO4/O2 and Na2SO4/1 percent SO2-O2 were performed. In the Na2SO4/O2 case, the cordierite reacted to form NaAlSiO4. After several hours of corrosion, the Na2SO4 appeared to induce surface cracks in the cordierite. In the Na2SO4/1 percent SO2-O2 case, other dissolution reactions occurred. The material was also tested in a burner rig with No. 2 Diesel fuel and 2 ppm sodium. The corrosion process was similar to that observed in the Na2SO4/O2 furnace tests, with more severe attack occurring.

Appropriate Mechanochemical Conditions for Corrosion-Fatigue Testing of Magnesium Alloys for Temporary Bioimplant Applications

NASA Astrophysics Data System (ADS)

Harandi, Shervin Eslami; Singh Raman, R. K.

2015-05-01

Magnesium (Mg) alloys possess great potential as bioimplants. A temporary implant employed as support for the repair of a fractured bone must possess sufficient strength to maintain their mechanical integrity for the required duration of healing. However, Mg alloys are susceptible to sudden cracking or fracture under the simultaneous action of cyclic loading and the corrosive physiological environment, i.e., corrosion fatigue (CF). Investigations of such fracture should be performed under appropriate mechanochemical conditions that appropriately simulate the actual human body conditions. This article reviews the existing knowledge on CF of Mg alloys in simulated body fluid and describes a relatively more accurate testing procedure developed in the authors' laboratory.

Crack injection in silver gold alloys

NASA Astrophysics Data System (ADS)

Chen, Xiying

Stress corrosion cracking (SCC) is a materials degradation phenomena resulting from a combination of stress and a corrosive environment. Among the alphabet soup of proposed mechanism of SCC the most important are film-rupture, film-induced cleavage and hydrogen embrittlement. This work examines various aspects of film-induced cleavage in gold alloys for which the operation of hydrogen embrittlement processes can be strictly ruled out on thermodynamic grounds. This is so because in such alloys SCC occurs under electrochemical conditions within which water is stable to hydrogen gas evolution. The alloy system examined in this work is AgAu since the corrosion processes in this system occur by a dealloying mechanism that results in the formation of nanoporous gold. The physics behind the dealloying process as well as the resulting formation of nanoporous gold is today well understood. Two important aspects of the film-induced cleavage mechanism are examined in this work: dynamic fracture in monolithic nanoporous gold and crack injection. In crack injection there is a finite thickness dealloyed layer formed on a AgAu alloy sample and the question of whether or not a crack that nucleates within this layer can travel for some finite distance into the un-corroded parent phase alloy is addressed. Dynamic fracture tests were performed on single edge-notched monolithic nanoporous gold samples as well as "infinite strip" sample configurations for which the stress intensity remains constant over a significant portion of the crack length. High-speed photography was used to measure the crack velocity. In the dynamic fracture experiments cracks were observed to travel at speeds as large as 270 m/s corresponding to about 68% of the Raleigh wave velocity. Crack injection experiments were performed on single crystal Ag77Au23, polycrystalline Ag72Au28 and pure gold, all of which had thin nanoporous gold layers on the surface of samples. Through-thickness fracture was seen in both the single crystal and polycrystalline samples and there was an indication of ~ 1 mum injected cracks into pure gold. These results have important implications for the operation of the film-induced cleavage mechanism and represent a first step in the development of a fundamental model of SCC.

Corrosion Product Film-Induced Stress Facilitates Stress Corrosion Cracking

PubMed Central

Wang, Wenwen; Zhang, Zhiliang; Ren, Xuechong; Guan, Yongjun; Su, Yanjing

2015-01-01

Finite element analyses were conducted to clarify the role of corrosion product films (CPFs) in stress corrosion cracking (SCC). Flat and U-shaped edge-notched specimens were investigated in terms of the CPF-induced stress in the metallic substrate and the stress in the CPF. For a U-shaped edge-notched specimen, the stress field in front of the notch tip is affected by the Young’s modulus of the CPF and the CPF thickness and notch geometry. The CPF-induced tensile stress in the metallic substrate is superimposed on the applied load to increase the crack tip strain and facilitate localized plasticity deformation. In addition, the stress in the CPF surface contributes to the rupture of the CPFs. The results provide physical insights into the role of CPFs in SCC. PMID:26066367

Electrochemical model of local corrosion at the tip of a loaded crack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreikiv, O.E.; Tym`yak, N.I.

1994-07-01

A model of electrochemical processes near a crack tip in a stressed metal subjected to corrosion with hydrogen depolarization is suggested. It is shown that, in order to describe the kinetics of hydrogenation of the prefracture area, it is necessary to take into account the type of passivation layer on the newly formed metal surface near the crack tip and the mechanism of its formation.

Chemical milling solution reveals stress corrosion cracks in titanium alloy

NASA Technical Reports Server (NTRS)

Braski, D. N.

1967-01-01

Solution of hydrogen flouride, hydrogen peroxide, and water reveals hot salt stress corrosion cracks in various titanium alloys. After the surface is rinsed in water, dried, and swabbed with the solution, it can be observed by the naked eye or at low magnification.

77 FR 37770 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-25

... repetitive inspections for cracking, corrosion damage, and any other irregularity of the lower main sill... 3187). That NPRM proposed to require repetitive inspections for cracking, corrosion damage, and any... agree that clarification is needed. Other ADs require inspections of certain structure covered by this...

Stress corrosion behavior of Ru-enhanced alpha-beta titanium alloys in methanol solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schutz, R.W.; Horrigan, J.M.; Bednarowicz, T.A.

1998-12-31

Conservative, practical guidelines for the minimum water content required to prevent methanolic stress corrosion cracking (SCC) of Ti-6Al-4V-Ru and Ti-3Al-2.5V-Ru alloy tubulars have been developed from slow strain rate testing in plain and acidified NaCl-saturated methanol-water solutions at 25 C. A minimum methanol water content of 10 wt.% is proposed for Ti-6Al-4V-Ru, whereas 2-3 wt.% is sufficient for the lower strength Ti-3Al-2.5V-Ru alloy. Although HCl-acidification aggravated methanolic SCC, intermixing of methanol with crude oil or pure hydrocarbons, H{sub 2}S gas saturation, and/or increasing temperature diminished cracking susceptibility in these alloy tubulars.

Influence of circumferential notch and fatigue crack on the mechanical integrity of biodegradable magnesium-based alloy in simulated body fluid.

PubMed

Bobby Kannan, M; Singh Raman, R K; Witte, F; Blawert, C; Dietzel, W

2011-02-01

Applications of magnesium alloys as biodegradable orthopaedic implants are critically dependent on the mechanical integrity of the implant during service. In this study, the mechanical integrity of an AZ91 magnesium alloy was studied using a constant extension rate tensile (CERT) method. The samples in two different geometries that is, circumferentially notched (CN), and circumferentially notched and fatigue cracked (CNFC), were tested in air and in simulated body fluid (SBF). The test results show that the mechanical integrity of the AZ91 magnesium alloy decreased substantially (∼50%) in both the CN and CNFC samples exposed to SBF. Fracture surface analysis revealed secondary cracks suggesting stress corrosion cracking susceptibility of the alloy in SBF. Copyright © 2010 Wiley Periodicals, Inc.

Evaluation of thiosulfate as a substitute for hydrogen sulfide in sour corrosion fatigue studies

NASA Astrophysics Data System (ADS)

Kappes, Mariano Alberto

This work evaluates the possibility of replacing hydrogen sulfide (H 2S) with thiosulfate anion (S2O32- ) in sour corrosion fatigue studies. H2S increases the corrosion fatigue crack growth rate (FCGR) and can be present in carbon steel risers and flowlines used in off-shore oil production. Corrosion tests with gaseous H2S require special facilities with safety features, because H2S is a toxic and flammable gas. The possibility of replacing H2S with S2O32-, a non-toxic anion, for studying stress corrosion cracking of stainless and carbon steels in H2S solutions was first proposed by Tsujikawa et al. ( Tsujikawa et al., Corrosion, 1993. 49(5): p. 409-419). In this dissertation, Tsujikawa work will be extended to sour corrosion fatigue of carbon steels. H2S testing is often conducted in deareated condition to avoid oxygen reaction with sulfide that yields sulfur and to mimic oil production conditions. Nitrogen deareation was also adopted in S2O3 2- testing, and gas exiting the cell was forced through a sodium hydroxide trap. Measurements of the sulfide content of this trap were used to estimate the partial pressure of H2S in nitrogen, and Henry's law was used to estimate the content of H2S in the solution in the cell. H2S was produced by a redox reaction of S2O 32-, which required electrons from carbon steel corrosion. This reaction is spontaneous at the open circuit potential of steel. Therefore, H2S concentration was expected to be maximum at the steel surface, and this concentration was estimated by a mass balance analysis. Carbon steel specimens exposed to S2O32- containing solutions developed a film on their surface, composed by iron sulfide and cementite. The film was not passivating and a good conductor of electrons. Hydrogen permeation experiments proved that this film controls the rate of hydrogen absorption of steels exposed to thiosulfate containing solutions. The absorption of hydrogen in S2O3 2- solutions was compared with the absorption of hydrogen in solutions saturated with different H2S partial pressures. The partial pressure was selected so that the concentration of H2S in the solution saturated with the gas would be the same as that reached in the surface of steel freely corroding in the thiosulfate solution. For solutions obtained by bubbling H2S, the rate of hydrogen absorption increased with the partial pressure of the gas, but the rate of hydrogen absorption reached a maximum at 10-3 M S2O3 2-, despite the surface concentration of H2S increased with the concentration of S2O32-. This effect was associated with the formation of thicker films, which inhibited the absorption of hydrogen. FCGR were evaluated at constant stress intensity factor range. Crack length was monitored in-situ by the direct current potential drop (DCPD) method. FCGR increased with the partial pressure of H2S in nitrogen. FCGR was controlled not only by the amount of hydrogen present in the steel, but also by inhibiting contributions like crack closure and crack tip blunting. FCGR in dilute thiosulfate solutions was near that measured in a solution saturated with a partial pressure of H2S equal to 0.56 kPa, in accord with hydrogen permeation results.

Corrosion fatigue crack propagation in metals

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.

1990-01-01

This review assesses fracture mechanics data and mechanistic models for corrosion fatigue crack propagation in structural alloys exposed to ambient temperature gases and electrolytes. Extensive stress intensity-crack growth rate data exist for ferrous, aluminum and nickel based alloys in a variety of environments. Interactive variables (viz., stress intensity range, mean stress, alloy composition and microstructure, loading frequency, temperature, gas pressure and electrode potential) strongly affect crack growth kinetics and complicate fatigue control. Mechanistic models to predict crack growth rates were formulated by coupling crack tip mechanics with occluded crack chemistry, and from both the hydrogen embrittlement and anodic dissolution/film rupture perspectives. Research is required to better define: (1) environmental effects near threshold and on crack closure; (2) damage tolerant life prediction codes and the validity of similitude; (3) the behavior of microcrack; (4) probes and improved models of crack tip damage; and (5) the cracking performance of advanced alloys and composites.

A Micro-Mechanism-Based Continuum Corrosion Fatigue Damage Model for Steels

NASA Astrophysics Data System (ADS)

Sun, Bin; Li, Zhaoxia

2018-05-01

A micro-mechanism-based corrosion fatigue damage model is developed for studying the high-cycle corrosion fatigue of steel from multi-scale viewpoint. The developed physical corrosion fatigue damage model establishes micro-macro relationships between macroscopic continuum damage evolution and collective evolution behavior of microscopic pits and cracks, which can be used to describe the multi-scale corrosion fatigue process of steel. As a case study, the model is used to predict continuum damage evolution and number density of the corrosion pit and short crack of steel component in 5% NaCl water under constant stress amplitude at 20 kHz, and the numerical results are compared with experimental results. It shows that the model is effective and can be used to evaluate the continuum macroscopic corrosion fatigue damage and study microscopic corrosion fatigue mechanisms of steel.

A Micro-Mechanism-Based Continuum Corrosion Fatigue Damage Model for Steels

NASA Astrophysics Data System (ADS)

Sun, Bin; Li, Zhaoxia

2018-04-01

A micro-mechanism-based corrosion fatigue damage model is developed for studying the high-cycle corrosion fatigue of steel from multi-scale viewpoint. The developed physical corrosion fatigue damage model establishes micro-macro relationships between macroscopic continuum damage evolution and collective evolution behavior of microscopic pits and cracks, which can be used to describe the multi-scale corrosion fatigue process of steel. As a case study, the model is used to predict continuum damage evolution and number density of the corrosion pit and short crack of steel component in 5% NaCl water under constant stress amplitude at 20 kHz, and the numerical results are compared with experimental results. It shows that the model is effective and can be used to evaluate the continuum macroscopic corrosion fatigue damage and study microscopic corrosion fatigue mechanisms of steel.

Validation of the role of bulk charging of hydrogen in the corrosion fatigue cracking of a low alloy steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griffiths, A.J.; Hutchings, R.B.; Turnbull, A.

1993-09-01

The enhanced corrosion fatigue crack growth rates of low alloy steels cathodically protected in marine environments results from absorbed hydrogen atoms. Hydrogen atoms are generated at the crack tip, crack walls and the external surface of the specimen (bulk charging). In previous work, Turnbull and Saenz de Santa Maria developed a model to predict the rate of generation of hydrogen atoms at the tips of fatigue cracks for steels cathodically polarized in marine environments. The main prediction from this work was that the external surface of the specimen can be the dominant source of hydrogen atoms at potentials more negativemore » than about [minus]900 mV (SCE), at a cyclic frequency of 0.1 Hz and a stress ratio of 0.5. The relative importance of bulk charging depends on the specific test conditions and is influenced by the applied potential, bulk chemistry, cyclic frequency, specimen thickness, temperature and use of coatings. Since laboratory test times are usually short in relation to the time required for hydrogen transport measured crack growth rates may be lower than those occurring in practice, for which there is sufficient time for full hydrogen charging. The purpose of this study is to verify experimentally the importance of bulk charging. Since the sensitivity of cracking to variations in hydrogen concentration will be material dependent a high strength steel was selected in this initial study because of its sensitivity to hydrogen. This will enable validation of the basic premise that bulk charging can be important, prior to more extensive studies using lower strength alloys.« less

The role of grain boundary chemistry and structure in the environmentally-assisted intergranular cracking of nickel-base alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Was, G.S.

1992-07-01

Stress corrosion cracking tests in constant extension rate tensile (CERT) and constant load tensile (CLT) tests were conducted on Ni-xCr- 9Fe-yC in Ar, water, and a LiOH-boric acid solution. Cr and C improve the resistance of Ni-base alloys to IG cracking in both Ar and water at 360C. Since creep plays a role in IG cracking, one possible explanation for the role of the environment involves its effect on the creep. Experiments were conducted on the role of C in the deformation behavior and failure mode of Ni-16Cr-9Fe. Constant load experiments were conducted on Ni-16Cr-9Fe to determine if the CLTmore » test is more aggressive than CERT. The electron backscattering technique in a SEM is being developed in order to extend the IG cracking studies to grain sizes typical of commercial alloys, 20-30 microns.« less

The role of grain boundary chemistry and structure in the environmentally-assisted intergranular cracking of nickel-base alloys. Progress report, August 1, 1991--July 31, 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Was, G.S.

1992-07-01

Stress corrosion cracking tests in constant extension rate tensile (CERT) and constant load tensile (CLT) tests were conducted on Ni-xCr- 9Fe-yC in Ar, water, and a LiOH-boric acid solution. Cr and C improve the resistance of Ni-base alloys to IG cracking in both Ar and water at 360C. Since creep plays a role in IG cracking, one possible explanation for the role of the environment involves its effect on the creep. Experiments were conducted on the role of C in the deformation behavior and failure mode of Ni-16Cr-9Fe. Constant load experiments were conducted on Ni-16Cr-9Fe to determine if the CLTmore » test is more aggressive than CERT. The electron backscattering technique in a SEM is being developed in order to extend the IG cracking studies to grain sizes typical of commercial alloys, 20-30 microns.« less

A Meta-Analysis Of Corrosion Studies for Maritime Patrol and Reconnaissance Aircraft (MPRA)

DTIC Science & Technology

2016-09-01

performed onsite. Aircraft rating was based upon the presence and/or extent of paint adhesion, paint cracking , clean ability, fluid damage, oxidation...because of corrosion control maintenance. No significant issues were observed related to paint cracking , fluid damage, corrosion, and clean ability of...HEXAMETHYLENEDIISOCYANATE 822-06-0 83194 X-310A; POLYURETHANE CATALYST XYLENE 1330-20-7 82649 X-530; HS EPOXY ENAMEL CURING SOLUTION BUTANOL 71-36-3

Effect of Sensitization on Corrosion-Fatigue Cracking in Al 5083 Alloy

DTIC Science & Technology

2015-01-21

Report Corrosion-fatigue Stress-corrosion cracking Aluminum alloys Sensitization October 2011 – September 2014 63-2634-A4 Unclassified Unlimited... alloy 5083-H131 is an armor-grade aluminum alloy that is non-heat-treatable and derives its strength from magnesium solute hardening and strain hardening...marine environments (references1-2). Even though the damaging effect of grain boundary β and sensitization on SCC in 5 -series aluminum alloys is

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Ziqing; Kruska, Karen; Toloczko, Mychailo B.

Stress corrosion crack initiation of two thermally-treated, cold-worked (CW) alloy 690 materials was investigated in 360oC simulated PWR primary water using constant load tensile (CLT) tests and blunt notch compact tension (BNCT) tests equipped with direct current potential drop (DCPD) for in-situ detection of cracking. SCC initiation was not detected by DCPD for the 21% and 31%CW CLT specimens loaded at their yield stress after ~9,220 h, however intergranular (IG) precursor damage and isolated surface cracks were observed on the specimens. The two 31%CW BNCT specimens loaded at moderate stress intensity after several cyclic loading ramps showed DCPD-indicated crack initiationmore » after 10,400h exposure at constant stress intensity, which resulted from significant growth of IG cracks. The 21%CW BNCT specimens only exhibited isolated small IG surface cracks and showed no apparent DCPD change throughout the test. Interestingly, post-test cross-section examinations revealed many grain boundary (GB) nano-cavities in the bulk of all the CLT and BNCT specimens particularly for the 31%CW materials. Cavities were also found along GBs extending to the surface suggesting an important role in crack nucleation. This paper provides an overview of the evolution of GB cavities and will discuss their effects on crack initiation in CW alloy 690.« less

A mechanical property and stress corrosion evaluation of 431 stainless steel alloy

NASA Technical Reports Server (NTRS)

Montano, J. W.

1973-01-01

The mechanical properties of type 431 stainless steel in two conditions: annealed bar and hardened and tempered bar are presented. Test specimens, manufactured from approximately 1.0 inch (2.54 cm) diameter bar stock, were tested at temperatures of 80 F (+26.7 C), 0 F (-17.8 C), -100 F (-73 C), and -200 F (-129 C). The test data indicated excellent tensile strength, notched/unnotched tensile ratio, ductility, shear, and impact properties at all testing temperatures. Results of the alternate immersion stress corrosion tests on stressed and unstressed longitudinal tensile specimens 0.1250 inch (0.3175 cm) diameter and transverse C-ring specimens, machined from 1.0 inch (2.54 cm) diameter bar stock, indicated that the material is not susceptible to stress corrosion cracking when tested in a 3.5 percent NaCl solution for 180 days.

The Corrosion and Corrosion Fatigue Behavior of Nickel Based Alloy Weld Overlay and Coextruded Claddings

NASA Astrophysics Data System (ADS)

Stockdale, Andrew

The use of low NOx boilers in coal fired power plants has resulted in sulfidizing corrosive conditions within the boilers and a reduction in the service lifetime of the waterwall tubes. As a solution to this problem, Ni-based weld overlays are used to provide the necessary corrosion resistance however; they are susceptible to corrosion fatigue. There are several metallurgical factors which give rise to corrosion fatigue that are associated with the localized melting and solidification of the weld overlay process. Coextruded coatings offer the potential for improved corrosion fatigue resistance since coextrusion is a solid state coating process. The corrosion and corrosion fatigue behavior of alloy 622 weld overlays and coextruded claddings was investigated using a Gleeble thermo-mechanical simulator retrofitted with a retort. The experiments were conducted at a constant temperature of 600°C using a simulated combustion gas of N2-10%CO-5%CO2-0.12%H 2S. An alternating stress profile was used with a minimum tensile stress of 0 MPa and a maximum tensile stress of 300 MPa (ten minute fatigue cycles). The results have demonstrated that the Gleeble can be used to successfully simulate the known corrosion fatigue cracking mechanism of Ni-based weld overlays in service. Multilayer corrosion scales developed on each of the claddings that consisted of inner and outer corrosion layers. The scales formed by the outward diffusion of cations and the inward diffusion of sulfur and oxygen anions. The corrosion fatigue behavior was influenced by the surface finish and the crack interactions. The initiation of a large number of corrosion fatigue cracks was not necessarily detrimental to the corrosion fatigue resistance. Finally, the as-received coextruded cladding exhibited the best corrosion fatigue resistance.

Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking

DOEpatents

Steeves, Arthur F.; Stewart, James C.

1981-01-01

A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.

Effect of CT Specimen Thickness on the Mechanical Characteristics at the Crack Tip of Stress Corrosion Cracking in Ni-based Alloys

NASA Astrophysics Data System (ADS)

Yinghao, Cui; He, Xue; Lingyan, Zhao

2017-12-01

It’s important to obtain accurate stress corrosion crack(SCC) growth rate for quantitative life prediction of components in nuclear power plants. However, the engineering practice shows that the crack tip constraint effect has a great influence on the mechanical properties and crack growth rate of SCC at crack tip. To study the influence of the specimen thickness on the crack tip mechanical properties of SCC, the stress, strain and C integral at creep crack tip are analyzed under different specimens thickness. Results show that the cracked specimen is less likely to crack due to effect of crack tip constraint. When the thickness ratio B/W is larger than 0.1, the crack tip constraint is almost ineffective. Value of C integral is the largest when B/W is 0.25. Then specimen thickness has little effect on the value of C integral. The effect of specimen thickness on the value of C integral is less significant at higher thickness ratio.

Effect of initial hydrogen content of a titanium alloy on susceptibility to hot-salt stress-corrosion

NASA Technical Reports Server (NTRS)

Gray, H. R.

1971-01-01

The Ti-8Al-1Mo-1V alloy was tested in four conditions: mill annealed (70 ppM H), duplex annealed (70 ppM H), vacuum annealed to an intermediate (36 ppM) and a low (9 ppM H) hydrogen level. Material annealed at 650 C (duplex condition) exhibited resistance to hot-salt stress corrosion superior to that exhibited by material in the mill-annealed condition. Reduction of the alloy hydrogen content from 70 to as low as 9 ppM did not influence resistance to hot-salt stress corrosion embrittlement or cracking.

Fundamental investigation of stress corrosion cracking

NASA Technical Reports Server (NTRS)

Beck, T. R.; Blackburn, M. J.; Smyrl, W. H.

1972-01-01

Two principle areas studied were stress corrosion crack growth rates of a titanium alloy in liquid environments containing halide ions and pitting corrosion of titanium in bromide solutions. Two initial assumptions were made, that the rate of propagation was controlled by a macroscopic solution parameter and that this parameter was viscosity. A series of solutions were prepared using lithium chloride as the solute and water, methanol, glycerin, formic acid, acetone, dimethyl sulphoxide, etc. As solvents, these solutions were prepared with a 5:1 solvent-solute ratio. Viscosity was varied by changing the temperature and it was found: (1) In all solvents the velocity of cracking was proportional to the reciprocal of the viscosity. (2) Each solvent gave a separate relationship, (3) The temperature dependence and numerical values for the apparent activation energy of cracking and viscosity were the same.

Stress Corrosion Cracking of Ferritic Materials for Fossil Power Generation Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J; Siefert, John A.

2014-01-01

Creep strength enhanced ferritic (CSEF) steels Grades 23, 24, 91, and 92 have been widely implemented in the fossil fired industry for over two decades. The stress corrosion cracking (SCC) behavior of these materials with respect to mainstay Cr-Mo steels (such as Grades 11, 12 and 22) has not been properly assessed, particularly in consideration of recent reported issues of SCC in CSEF steels. This report details the results of Jones test exposures of a wide range of materials (Grades 11, 22, 23, 24, and 92), material conditions (as-received, improper heat treatments, normalized, weldments) and environments (salt fog; tube cleaningmore » environments including decreasing, scale removal, and passivation; and high temperature water) to compare the susceptibility to cracking of these steels. In the as-received (normalized and tempered) condition, none of these materials are susceptible to SCC in the environments examined. However, in the hardened condition, certain combinations of environment and alloy reveal substantial SCC susceptibility.« less

Interface between fatigue, creep and stress-corrosion cracking on Ti6246 titanium alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarrazin-Baudoux, C.; Chabanne, Y.; Petit, J.

1999-07-01

The influence of mean stress on the fatigue crack growth behavior of a Ti6246 alloy has been studied in the near-threshold area at room temperature and at 500 C. Tests were performed at various constant K{sub max} levels in ambient air, high vacuum and humidified Argon. Conditions for the occurrence of an abnormal behavior consisting in the disappearance of the threshold for sufficiently high K{sub max} level, are discussed with respect to environment and temperature. This effect is observed in air and in vacuum for K{sub max} higher than 52 MPa{radical}m, and is related to an intrinsic creep damage processmore » which appears more efficient at room temperature than at 500 C and more accentuated in air than in vacuum. In humidified Argon, the critical Kmax level is reduced at 22 MPa{radical}m at 500 C, such a detrimental effect being related to a Stress Corrosion Cracking process induced by water vapor.« less

Corrosion Behavior of Steel Reinforcement in Concrete with Recycled Aggregates, Fly Ash and Spent Cracking Catalyst.

PubMed

Gurdián, Hebé; García-Alcocel, Eva; Baeza-Brotons, Francisco; Garcés, Pedro; Zornoza, Emilio

2014-04-21

The main strategy to reduce the environmental impact of the concrete industry is to reuse the waste materials. This research has considered the combination of cement replacement by industrial by-products, and natural coarse aggregate substitution by recycled aggregate. The aim is to evaluate the behavior of concretes with a reduced impact on the environment by replacing a 50% of cement by industrial by-products (15% of spent fluid catalytic cracking catalyst and 35% of fly ash) and a 100% of natural coarse aggregate by recycled aggregate. The concretes prepared according to these considerations have been tested in terms of mechanical strengths and the protection offered against steel reinforcement corrosion under carbonation attack and chloride-contaminated environments. The proposed concrete combinations reduced the mechanical performance of concretes in terms of elastic modulus, compressive strength, and flexural strength. In addition, an increase in open porosity due to the presence of recycled aggregate was observed, which is coherent with the changes observed in mechanical tests. Regarding corrosion tests, no significant differences were observed in the case of the resistance of these types of concretes under a natural chloride attack. In the case of carbonation attack, although all concretes did not stand the highly aggressive conditions, those concretes with cement replacement behaved worse than Portland cement concretes.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE PAGES

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.; ...

2017-11-26

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300–360 °C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N 2 gas. Lastly, results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Characterization of microstructure, local deformation and microchemistry in Alloy 690 heat-affected zone and stress corrosion cracking in high temperature water

NASA Astrophysics Data System (ADS)

Lu, Zhanpeng; Chen, Junjie; Shoji, Tetsuo; Takeda, Yoichi; Yamazaki, Seiya

2015-10-01

With increasing the distance from the weld fusion line in an Alloy 690 heat-affected zone, micro-hardness decreases, kernel average misorientation decreases and the fraction of Σ3 boundaries increases. Chromium depletion at grain boundaries in the Alloy 690 heat-affected zone is less significant than that in an Alloy 600 heat-affected zone. Alloy 690 heat-affected zone exhibits much higher IGSCC resistance than Alloy 600 heat-affected zone in simulated pressurized water reactor primary water. Heavily cold worked Alloy 690 exhibits localized intergranular stress corrosion cracking. The effects of metallurgical and mechanical properties on stress corrosion cracking in Alloy 690 are discussed.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300–360 °C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N 2 gas. Lastly, results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300-360°C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N2 gas. Results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

An Electrochemical Framework to Explain Intergranular Stress Corrosion Cracking in an Al-5.4%Cu-0.5%Mg-0.5%Ag Alloy

NASA Technical Reports Server (NTRS)

Little, D. A.; Connolly, B. J.; Scully, J. R.

2001-01-01

A modified version of the Cu-depletion electrochemical framework was used to explain the metallurgical factor creating intergranular stress corrosion cracking susceptibility in an aged Al-Cu-Mg-Ag alloy, C416. This framework was also used to explain the increased resistance to intergranular stress corrosion cracking in the overaged temper. Susceptibility in the under aged and T8 condition is consistent with the grain boundary Cu-depletion mechanism. Improvements in resistance of the T8+ thermal exposure of 5000 h at 225 F (T8+) compared to the T8 condition can be explained by depletion of Cu from solid solution.

Characterization of stress corrosion cracks in Ni-based weld alloys 52, 52M and 152 grown in high-temperature water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yi; Wu, Yaqiao; Burns, Jatuporn

Ni-based weld alloys 52, 52M and 152 are extensively used in repair and mitigation of primary water stress corrosion cracking (SCC) in nuclear power plants. In the present study, a series of microstructure and microchemistry at the SCC tips of these alloys were examined with scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (STEM) and energy filtered transmission electron microscopy (EFTEM). The specimens have similar chemical compositions and testing conditions. Intergranular (IG) and transgranular (TG) SCC was observed in all of them. The cracks were filled with nickel-oxidesmore » and partial precipitations of chrome carbides (CrCs), niobium carbides (NbCs), titanium nitrides (TiNs) and silicon carbides (SiCs), while iron (Fe) was largely dissolved into the solution. However, the crack densities, lengths and distributions were different for all three specimens. - Highlights: • Microstructure and microchemistry at the SCC tips of Ni-based weld alloys 52, 52M and 152 were examined. • The crack densities, lengths and distributions were found to be different for different alloys. • IGSCC and TGSCC were observed on alloy 52, only TGSCC was observed on alloy 52M and 152. • The cracks were filled by Ni-oxides and precipitated CrCs, NbCs, TiNs and SiCs.« less

Corrosion behavior and mechanical properties of bioactive sol-gel coatings on titanium implants.

PubMed

Catauro, M; Bollino, F; Papale, F; Giovanardi, R; Veronesi, P

2014-10-01

Organic-inorganic hybrid coatings based on zirconia and poly (ε-caprolactone) (PCL) were prepared by means of sol-gel dip-coating technique and used to coat titanium grade 4 implants (Ti-4) in order to improve their wear and corrosion resistance. The coating chemical composition has been analysed by ATR-FTIR. The influence of the PCL amount has been investigated on the microstructure, mechanical properties of the coatings and their ability to inhibit the corrosion of titanium. SEM analysis has shown that all coatings have a nanostructured nature and that the films with high PCL content are crack-free. Mechanical properties of the coatings have been studied using scratch and nano-indentation tests. The results have shown that the Young's modulus of the coatings decreases in presence of large amounts of the organic phase, and that PCL content affects also the adhesion of the coatings to the underlying Ti-4 substrate. However, the presence of cracks on the PCL-free coatings affects severely the mechanical response of the samples at high loads. The electrochemical behavior and corrosion resistance of the coated and uncoated substrate has been investigated by polarization tests. The results have shown that both the coatings with or without PCL don't affect significantly the already excellent passivation properties of titanium. Copyright © 2014. Published by Elsevier B.V.

Evaluating stress corrosion cracking behaviour of high strength AA7075-T651 aluminium alloy

NASA Astrophysics Data System (ADS)

Prabhuraj, P.; Rajakumar, S.; Lakshminarayanan, A. K.; Balasubramanian, V.

2017-12-01

The objective of the present study is to determine the threshold stress level of stress corrosion cracking (SCC) in AA7075-T651 aluminium alloy by suitable experimentation. The test was carried out using a circumferential notch specimen in a horizontal-type constant load SCC setup in a 3.5 wt.% NaCl solution. The time to failure by SCC was determined at various loading conditions. The threshold stress of AA7075-T651 alloy was found to be 242 MPa in a 3.5 wt.% NaCl solution. The various regions of the fractured surface specimen such as machined notch, SCC region and final overload fracture area were examined using scanning electron microscopy (SEM) in order to identify the SCC mechanism.

The breaking load method - Results and statistical modification from the ASTM interlaboratory test program

NASA Technical Reports Server (NTRS)

Colvin, E. L.; Emptage, M. R.

1992-01-01

The breaking load test provides quantitative stress corrosion cracking data by determining the residual strength of tension specimens that have been exposed to corrosive environments. Eight laboratories have participated in a cooperative test program under the auspices of ASTM Committee G-1 to evaluate the new test method. All eight laboratories were able to distinguish between three tempers of aluminum alloy 7075. The statistical analysis procedures that were used in the test program do not work well in all situations. An alternative procedure using Box-Cox transformations shows a great deal of promise. An ASTM standard method has been drafted which incorporates the Box-Cox procedure.

Surface Studies of Ultra Strength Drilling Steel after Corrosion Fatigue in Simulated Sour Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. Ziomek-Moroz; J.A. Hawk; R. Thodla

2012-05-06

The Unites States predicted 60% growth in energy demand by 2030 makes oil and natural gas primary target fuels for energy generation. The fact that the peak of oil production from shallow wells (< 5000 m) is about to be reached, thereby pushing the oil and natural gas industry into deeper wells. However, drilling to depths greater than 5000 m requires increasing the strength-to weight ratio of the drill pipe materials. Grade UD-165 is one of the ultra- high yield strength carbon steels developed for ultra deep drilling (UDD) activities. Drilling UDD wells exposes the drill pipes to Cl{sup -},more » HCO{sub 3}{sup -}/CO{sub 3}{sup 2-}, and H{sub 2}S-containig corrosive environments (i.e., sour environments) at higher pressures and temperatures compared to those found in conventional wells. Because of the lack of synergism within the service environment, operational stresses can result in catastrophic brittle failures characteristic for environmentally assisted cracking (EAC). Approximately 75% of all drill string failures are caused by fatigue or corrosion fatigue. Since there is no literature data on the corrosion fatigue performance of UD-165 in sour environments, research was initiated to better clarify the fatigue crack growth (FCGR) behavior of this alloy in UDD environments. The FCGR behavior of ultra-strength carbon steel, grade UD-165, was investigated by monitoring crack growth rate in deaerated 5%NaCl solution buffered with NaHCO{sub 3}/Na{sub 2}CO{sub 3} and in contact with H{sub 2}S. The partial pressure of H{sub 2}S (p{sub H2S}) was 0.83 kPa and pH of the solution was adjusted by NaOH to 12. The fatigue experiments were performed at 20 and 85 C in an autoclave with surface investigations augmented by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. In this study, research focused on surface analyses supported by the fatigue crack growth rate measurements. Fig. 1 shows an SEM micrograph of the crack that propagated from the notch in the solution at 20 C. Accumulation of the corrosion products is visible along the crack. The EDX chemical analysis near the crack tip found iron, sulfur and oxygen in the passive layer. The surface of the sample after the fatigue test in the sour environment at 85{sup o}, Fig. 2, C looks different from that fatigued surface at 20 C. The crack propagates across the passive film that covers the surface fairly uniformly. Some spallation of the passive film is observed near the notch. The EDX chemical analysis of the passive film near the crack tip identified mainly iron, carbon and oxygen. It appears that temperature plays a very important role in formation of the passive film. This may be associated with different solubility of H{sub 2}S in the solution, which will be further studied.« less

Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking

DOEpatents

Not Available

1980-05-28

A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking is described. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.

77 FR 13228 - Airworthiness Directives; BAE SYSTEMS (Operations) Limited Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-06

... wing rear spar. This proposed AD would require a one-time detailed inspection for cracks, corrosion, and other defects of the rear face of the wing rear spar, and repair if necessary. We are proposing... above, this [EASA] AD requires a one- time [detailed] inspection [for cracks, corrosion, and other...

78 FR 57049 - Airworthiness Directives; the Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-17

... discrepancy other than cracking is found (e.g., corrosion) during any inspection required by paragraph (g) of... other than cracking is found (e.g., corrosion) during any inspection required by paragraph (h) of this... per hour = $255. nut type. According to the manufacturer, some of the costs of this AD may be covered...

Fatigue Testing of AA7050-T7451 with Various Corrosion Prevention Surface Treatments

DTIC Science & Technology

2013-06-01

UNCLASSIFIED Authors Marcus McDonald Air Vehicles Division Marcus McDonald initially spent 3 years working in the oil & gas, steel and...treatments: caustic degreasing, de-oxidising or anodising. The pits in the anodised coupons were larger than the pits caused by the pre-IVD etching...those fatigue cracks that grew from them spent less time in growing whilst they were small, because the crack started at what was a larger effective

Inverse problems in eddy current testing using neural network

NASA Astrophysics Data System (ADS)

Yusa, N.; Cheng, W.; Miya, K.

2000-05-01

Reconstruction of crack in conductive material is one of the most important issues in the field of eddy current testing. Although many attempts to reconstruct cracks have been made, most of them deal with only artificial cracks machined with electro-discharge. However, in the case of natural cracks like stress corrosion cracking or inter-granular attack, there must be contact region and therefore their conductivity is not necessarily zero. In this study, an attempt to reconstruct natural cracks using neural network is presented. The neural network was trained through numerical simulated data obtained by the fast forward solver that calculated unflawed potential data a priori to save computational time. The solver is based on A-φ method discretized by using FEM-BEM A natural crack was modeled as an area whose conductivity was less than that of a specimen. The distribution of conductivity in that area was reconstructed as well. It took much time to train the network, but the speed of reconstruction was extremely fast after once it was trained. Well-trained network gave good reconstruction result.

A Survey of Corrosion and Conditions of Corrosion Protection Systems in Civil Works Structures of the U.S. Army Corps of Engineers

DTIC Science & Technology

2014-09-01

corrosion: coatings and cathodic protection (CP). Coatings consist of paints, epoxies, enamels , metalizing, and other coatings. CP is a chem- ical means...environmental factors such as water quality and resistivity. One of the major problems associated with lock gates is structural cracking in the...One of the problems described by Mr. Davis is fatigue crack growth resulting from the poor welding usually associated with stress risers and

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, J.C.; Van Konynenburg, R.A.; McCright, R.D.

1988-04-01

Three iron- to nickel-based austenitic alloys (Types 304L and 316L stainless steels and Alloy 825) are being considered as candidate materials for the fabrication of high-level radioactive-waste containers. Waste will include fuel assemblies from reactors as well as high-level waste in borosilicate glass forms, and will be sent to the prospective repository at Yucca Mountain, Nevada. The decay of radionuclides in the repository will result in the generation of substantial heat and in fluences of gamma radiation. Container materials may undergo any of several modes of degradation in this environment, including atmospheric oxidation; uniform aqueous phase corrosion; pitting; crevice corrosion;more » sensitization and intergranular stress corrosion cracking (IGSCC); and transgranular stress corrosion cracking (TGSCC). This report is an analysis of data relevant to the pitting, crevice corrosion, and stress corrosion cracking (SCC) of the three austenitic candidate alloys. The candidates are compared in terms of their susceptibilities to these forms of corrosion. Although all three candidates have demonstrated pitting and crevice corrosion in chloride-containing environments, Alloy 825 has the greatest resistance to these types of localized corrosion (LC); such resistance is important because pits can penetrate the metal and serve as crack initiation sites. Both Types 304L and 316L stainless steels are susceptible to SCC in acidic chloride media. In contrast, SCC has not been documented in Alloy 825 under comparable conditions. Gamma radiation has been found to enhance SCC in Types 304 and 304L stainless steels, but it has no detectable effect on the resistance of Alloy 825 to SCC. Furthermore, while the effects of microbiologically induced corrosion have been observed for 300-series stainless steels, nickel-based alloys such as Alloy 825 seem to be immune to such problems. 211 refs., 49 figs., 10 tabs.« less

Crack depth profiling using guided wave angle dependent reflectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volker, Arno, E-mail: arno.volker@tno.nl; Pahlavan, Lotfollah, E-mail: arno.volker@tno.nl; Blacquiere, Gerrit, E-mail: arno.volker@tno.nl

2015-03-31

Tomographic corrosion monitoring techniques have been developed, using two rings of sensors around the circumference of a pipe. This technique is capable of providing a detailed wall thickness map, however this might not be the only type of structural damage. Therefore this concept is expanded to detect and size cracks and small corrosion defects like root corrosion. The expanded concept uses two arrays of guided-wave transducers, collecting both reflection and transmission data. The data is processed such that the angle-dependent reflectivity is obtained without using a baseline signal of a defect-free situation. The angle-dependent reflectivity is the input of anmore » inversion scheme that calculates a crack depth profile. From this profile, the depth and length of the crack can be determined. Preliminary experiments show encouraging results. The depth sizing accuracy is in the order of 0.5 mm.« less

Oxide inclusions in laser additive manufactured stainless steel and their effects on impact toughness and stress corrosion cracking behavior

NASA Astrophysics Data System (ADS)

Lou, Xiaoyuan; Andresen, Peter L.; Rebak, Raul B.

2018-02-01

Intergranular and intragranular Si and Mn rich oxide inclusions are present in laser additive manufactured austenitic stainless steel. The uniform oxide dispersions in additive manufactured material promoted early initiation of microvoids and reduced its impact toughness relative to powder metallurgy (hot isostatic pressing) and wrought materials. For stress corrosion cracking in high temperature water, the silica inclusions along the grain boundaries preferentially dissolved and appeared to accelerate oxidation and caused extensive crack branching.

Effect of Low-Temperature Environment on Stress Corrosion Cracking Behavior of X80 Pipeline Steel in Simulated Alkaline Soil Solution

NASA Astrophysics Data System (ADS)

Xie, Fei; Wang, Dan; Wu, Ming; Yu, Chengxiang; Sun, Dongxu; Yang, Xu; Xu, Changhao

2018-04-01

The stress corrosion cracking (SCC) of X80 pipeline steel in simulated alkaline soil solution under different temperatures was investigated by slow-strain-rate testing, scanning electron microscopy and energy-dispersive spectroscopy. Results showed that the fracture was transgranular and brittle at 273 K to 278 K (0 °C to 5 °C), and the metal surface was dissolved by a large number of chloride ions. Furthermore, hydrogen embrittlement was caused by the hydrogen atom extended to the high-stress region. The fracture process was controlled by hydrogen-induced cracking, and SCC was highly sensitive at this stage. At 288 K to 298 K (15 °C to 25 °C), the fracture morphology was attributed to the mixed mode of ductile and brittle fractures, the fracture process was controlled by the mechanism of hydrogen-induced cracking and anodic dissolution, and the susceptibility to SCC decreased. When the temperature reached 308 K to 318 K (35 °C to 45 °C), the fracture was mainly intergranular and ductile, the fracture process was controlled by anodic dissolution, and SCC sensitivity was the smallest in this temperature range.

Corrosion Characterization in Nickel Plated 110 ksi Low Alloy Steel and Incoloy 925: An Experimental Case Study

NASA Astrophysics Data System (ADS)

Thomas, Kiran; Vincent, S.; Barbadikar, Dipika; Kumar, Shresh; Anwar, Rebin; Fernandes, Nevil

2018-04-01

Incoloy 925 is an age hardenable Nickel-Iron-Chromium alloy with the addition of Molybdenum, Copper, Titanium and Aluminium used in many applications in oil and gas industry. Nickel alloys are preferred mostly in corrosive environments where there is high concentration of H2S, CO2, chlorides and free Sulphur as sufficient nickel content provides protection against chloride-ion stress-corrosion cracking. But unfortunately, Nickel alloys are very expensive. Plating an alloy steel part with nickel would cost much lesser than a part make of nickel alloy for large quantities. A brief study will be carried out to compare the performance of nickel plated alloy steel with that of an Incoloy 925 part by conducting corrosion tests. Tests will be carried out using different coating thicknesses of Nickel on low alloy steel in 0.1 M NaCl solution and results will be verified. From the test results we can confirm that Nickel plated low alloy steel is found to exhibit fairly good corrosion in comparison with Incoloy 925 and thus can be an excellent candidate to replace Incoloy materials.

Strength and Durability of Fly Ash-Based Fiber-Reinforced Geopolymer Concrete in a Simulated Marine Environment

NASA Astrophysics Data System (ADS)

Martinez Rivera, Francisco Javier

This research is aimed at investigating the corrosion durability of polyolefin fiberreinforced fly ash-based geopolymer structural concrete (hereafter referred to as GPC, in contradistinction to unreinforced geopolymer concrete referred to as simply geopolymer concrete), where cement is completely replaced by fly ash, that is activated by alkalis, sodium hydroxide and sodium silicate. The durability in a marine environment is tested through an electrochemical method for accelerated corrosion. The GPC achieved compressive strengths in excess of 6,000 psi. Fiber reinforced beams contained polyolefin fibers in the amounts of 0.1%, 0.3%, and 0.5% by volume. After being subjected to corrosion damage, the GPC beams were analyzed through a method of crack scoring, steel mass loss, and residual flexural strength testing. Fiber reinforced GPC beams showed greater resistance to corrosion damage with higher residual flexural strength. This makes GPC an attractive material for use in submerged marine structures.

Eddy Current System for Material Inspection and Flaw Visualization

NASA Technical Reports Server (NTRS)

Bachnak, R.; King, S.; Maeger, W.; Nguyen, T.

2007-01-01

Eddy current methods have been successfully used in a variety of non-destructive evaluation applications including detection of cracks, measurements of material thickness, determining metal thinning due to corrosion, measurements of coating thickness, determining electrical conductivity, identification of materials, and detection of corrosion in heat exchanger tubes. This paper describes the development of an eddy current prototype that combines positional and eddy-current data to produce a C-scan of tested material. The preliminary system consists of an eddy current probe, a position tracking mechanism, and basic data visualization capability. Initial test results of the prototype are presented in this paper.

Reaction Control System Thruster Cracking Consultation: NASA Engineering and Safety Center (NESC) Materials Super Problem Resolution Team (SPRT) Findings

NASA Technical Reports Server (NTRS)

MacKay, Rebecca A.; Smith, Stephen W.; Shah, Sandeep R.; Piascik, Robert S.

2005-01-01

The shuttle orbiter s reaction control system (RCS) primary thruster serial number 120 was found to contain cracks in the counter bores and relief radius after a chamber repair and rejuvenation was performed in April 2004. Relief radius cracking had been observed in the 1970s and 1980s in seven thrusters prior to flight; however, counter bore cracking had never been seen previously in RCS thrusters. Members of the Materials Super Problem Resolution Team (SPRT) of the NASA Engineering and Safety Center (NESC) conducted a detailed review of the relevant literature and of the documentation from the previous RCS thruster failure analyses. It was concluded that the previous failure analyses lacked sufficient documentation to support the conclusions that stress corrosion cracking or hot-salt cracking was the root cause of the thruster cracking and lacked reliable inspection controls to prevent cracked thrusters from entering the fleet. The NESC team identified and performed new materials characterization and mechanical tests. It was determined that the thruster intergranular cracking was due to hydrogen embrittlement and that the cracking was produced during manufacturing as a result of processing the thrusters with fluoride-containing acids. Testing and characterization demonstrated that appreciable environmental crack propagation does not occur after manufacturing.

Intergranular tellurium cracking of nickel-based alloys in molten Li, Be, Th, U/F salt mixture

NASA Astrophysics Data System (ADS)

Ignatiev, Victor; Surenkov, Alexander; Gnidoy, Ivan; Kulakov, Alexander; Uglov, Vadim; Vasiliev, Alexander; Presniakov, Mikhail

2013-09-01

In Russia, R&D on Molten Salt Reactor (MSR) are concentrated now on fast/intermediate spectrum concepts which were recognized as long term alternative to solid fueled fast reactors due to their attractive features: strong negative feedback coefficients, easy in-service inspection, and simplified fuel cycle. For high-temperature MSR corrosion of the metallic container alloy in primary circuit is the primary concern. Key problem receiving current attention include surface fissures in Ni-based alloys probably arising from fission product tellurium attack. This paper summarizes results of corrosion tests conducted recently to study effect of oxidation state in selected fuel salt on tellurium attack and to develop means of controlling tellurium cracking in the special Ni-based alloys recently developed for molten salt actinide recycler and tranforming (MOSART) system. Tellurium corrosion of Ni-based alloys was tested at temperatures up to 750 °C in stressed and unloaded conditions in molten LiF-BeF2 salt mixture fueled by about 20 mol% of ThF4 and 2 mol% of UF4 at different [U(IV)]/[U(III)] ratios: 0.7, 4, 20, 100 and 500. Following Ni-based alloys (in mass%): HN80М-VI (Mo—12, Cr—7.6, Nb—1.5), HN80МТY (Mo—13, Cr—6.8, Al—1.1, Ti—0.9), HN80МТW (Mo—9.4, Cr—7.0, Ti—1.7, W—5.5) and ЕМ-721 (W—25.2, Cr—5.7, Ti—0.17) were used for the study in the corrosion facility. If the redox state the fuel salt is characterized by uranium ratio [U(IV)]/[U(III)] < 1 the alloys' specimens get a more negative stationary electrode potential than equilibrium electrode potentials of some uranium intermetallic compounds and alloys with nickel and molybdenum. This leads to spontaneous behavior of alloy formation processes on the specimens' surface and further diffusion of uranium deep into the metallic phase. As consequence of this films of intermetallic compounds and alloys of nickel, molybdenum, tungsten with uranium are formed on the alloys specimens' surface, and intergranular corrosion does not take place. In the fuel salt with [U(IV)]/[U(III)] = 4-20 the potentials of uranium alloy formation with the main components of the tested alloys are not reached, that's why alloys and intermetallic compounds are not formed on the surface of the investigated chromium-nickel alloys. Under such conditions any intergranular tellurium corrosion of the selected alloys does not occur. In the fuel salt with [U(IV)/]/[U(III)] = 100 the potentials of uranium alloy formation with the main components of the tested alloys are not also reached. Under such redox conditions any traces intergranular tellurium IGC on the HN80MTY and H80M-VI alloys specimens are not found. Certain signs of incipient IGC in the form of tellurium presence on the grain boundaries in the HN80MTB and EM-721 alloys surface layer and formation of not too deep cracks on HN80MTB alloy surface were revealed at [U(IV)/]/[U(III)] = 100. With this uranium ratio in the presence of corrosion products on the surface of all of the alloys films, containing tellurium, metals of the construction alloys and carbon, are formed. In the melt with [U(IV)]/[U(III)] = 500 in all of the alloys tested the tellurium IGC took place. The HN80MTY alloy shows the maximum resistance to tellurium IGC. The intensity of tellurium IGC of the alloy (the K parameter) is by 3-5 times lower as compared to other alloys. The EM-721 alloy has the minimal resistance to tellurium IGC (K = 9200 pc m/cm, the depth of cracks is up to 434 μm). The studies have shown, that the intensity of the nickel alloys IGC is controlled by the [U(IV)]/[U(III)] ratio, and its dependence on this parameter is of threshold character. Providing the uranium ratio value's monitoring and regulation, it is possible to control the tellurium corrosion and in such a way to eliminate IGC completely or to minimize its value. The alloys strength characteristics and their structure were changed insignificantly after testing within the [U(IV)]/[U(III)] range from 0.7 tо 100. The changes are not linked with the influence of fuel salt, containing tellurium additions, but are stipulated by alloys structure, temperature factor, exposure time and mechanical loads. Significant effect of tellurium cracking on the alloys (excepting HN80MTY) strength characteristics was established after corrosion testing with [U(IV)]/[U(III)] = 500. In the absence of IGC all of the alloys investigated have a good ductility at high strength characteristics. The disrupture of specimens under mechanical tests both before and after corrosion tests of all alloys except for ЕМ-721 proceeds on a ductile mechanism. On the EM-721 alloy specimens, both in their initial state and after corrosion testing, clear signs of brittle destruction, caused by heterogeneity of its structure due to the presence of tungsten phase, are very clearly observed. The presence of such phases increases the alloy IGC and leads to reduction of the alloy resistance tellurium damage. The HN80MTY alloy has the best corrosion and mechanical properties. It does not undergo tellurium IGC in the molten 75LiF-5BeF2-20ThF4 salt mixture fueled by about 2 mol% of UF4 with [U(IV)]/[U(III)] ratio ⩽ 100. The alloy has high resistance to tellurium cracking at [U(IV)]/[U(III)] = 500. The alloy can be recommended as the main construction material for the fuel circuit with selected salt composition up to temperature 750 °С.

Stress corrosion resistant fasteners

NASA Technical Reports Server (NTRS)

Roach, T. A.

1985-01-01

A family of high performance aerospace fasteners made from corrosion resistant alloys for use in applications where corrosion and stress-corrosion cracking are of major concern are discussed. The materials discussed are mainly A-286, Inconel 718, MP35N and MP159. Most of the fasteners utilize cold worked and aged materials to achieve the desired properties. The fasteners are unique in that they provide a combination of high strength and immunity to stress corrosion cracking not previously attainable. A discussion of fastener stress corrosion failures is presented including a review of the history and a description of the mechanism. Case histories are presented to illustrate the problems which can arise when material selection is made without proper regard for the environmental conditions. Mechanical properties and chemical compositions are included for the fasteners discussed. Several aspects of the application of high performance corrosion resistant fasteners are discussed including galvanic compatibility and torque-tension relationships.

Research at USAFA 2010

DTIC Science & Technology

2010-01-01

optical surveillance program for Space Situational Awareness (SSA), cadet First class Sean harte’s break-through repair technique for enamel ...also undertaken several collaborative projects to include Air Force Research Lab projects such as crack growth studies and a c-130 center Wingbox...research. the research projects involved in the collaboration include energy harvesting, corrosion and stress corrosion cracking of aging aircraft

75 FR 43803 - Airworthiness Directives; The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-27

... resulted from stress corrosion and pitting along the length of the spindle and spindle diameter, and... requirements would ensure that stress and pitting corrosion are detected and corrected, which would avoid... caused by fatigue. Because of the difficulty in detecting small cracks and the rapid crack growth in...

An automated tool-joint inspection device for the drillstring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moyer, M.C.; Dale, B.A.; Kusenberger, F.N.

1984-06-01

This paper discusses the development of an automated tool joint inspection device-i.e., the fatigue crack detector (FCD), which can detect defects in the threaded region of drillpipe and drill collars. Inspection tests conducted at a research test facility and at drilling rig sites indicate that this device can detect both simulated defects (saw slots and drilled holes) and service-induced defects, such as fatigue cracks, pin stretch (plastic deformation), mashed threads, and corrosion pitting. The system operates on an electromagnetic-flux leakage principle and has several advantages over the conventional method of magnetic particle inspection.

Layer texture of hot-rolled BCC metals and its significance for stress-corrosion cracking of main gas pipelines

NASA Astrophysics Data System (ADS)

Perlovich, Yu. A.; Isaenkova, M. G.; Krymskaya, O. A.; Morozov, N. S.

2016-10-01

Based on data of X-ray texture analysis of hot-rolled BCC materials it was shown that the layerwise texture inhomogeneity of products is formed during their manufacturing. The effect can be explained by saturation with interstitial impurities of the surface layer, resulting in dynamical deformation aging (DDA). DDA prevents the dislocation slip under rolling and leads to an increase of lattice parameters in the external layer. The degree of arising inhomogeneity correlates with the tendency of hot-rolled sheets and obtained therefrom tubes to stress-corrosion cracking under exploitation, since internal layers have a compressive effect on external layers, and prevents opening of corrosion cracks at the tube surface.

US/Australia Collaborative Research Project on Corrosion Fatigue in D6AC Steel Joints

DTIC Science & Technology

1978-12-01

Life of Exposure Groups at 80,000 psi Max Load Level (R=0.1) 77 10 Location of Observable Fatigue Cracks on Failed D6AC Steel Specimen Surfaces 78 11...ing the machining and assembly process. Such liquids might have a serious deleterious effect on the fatigue life of the aircraft. Further, there was...control tests were to provide a base for determining the various corrosion effects on fatigue life , and to deter- mine any differences in laboratory

Modeling of concrete cracking due to corrosion process of reinforcement bars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bossio, Antonio, E-mail: antonio.bossio@unina.it; Monetta, Tullio, E-mail: monetta@unina.it; Bellucci, Francesco, E-mail: bellucci@unina.it

The reinforcement corrosion in Reinforced Concrete (RC) is a major reason of degradation for structures and infrastructures throughout the world leading to their premature deterioration before design life was attained. The effects of corrosion of reinforcement are: (i) the reduction of the cross section of the bars, and (ii) the development of corrosion products leading to the appearance of cracks in the concrete cover and subsequent cover spalling. Due to their intrinsic complex nature, these issues require an interdisciplinary approach involving both material science and structural design knowledge also in terms on International and National codes that implemented the conceptmore » of durability and service life of structures. In this paper preliminary FEM analyses were performed in order to simulate pitting corrosion or general corrosion aimed to demonstrate the possibility to extend the results obtained for a cylindrical specimen, reinforced by a single bar, to more complex RC members in terms of geometry and reinforcement. Furthermore, a mechanical analytical model to evaluate the stresses in the concrete surrounding the reinforcement bars is proposed. In addition, a sophisticated model is presented to evaluate the non-linear development of stresses inside concrete and crack propagation when reinforcement bars start to corrode. The relationships between the cracking development (mechanical) and the reduction of the steel section (electrochemical) are provided. Finally, numerical findings reported in this paper were compared to experimental results available in the literature and satisfactory agreement was found.« less

Radiation chemistry related to nuclear power technology

NASA Astrophysics Data System (ADS)

Ishigure, Kenkichi

A brief review is given to the radiation chemical problems, especially with the emphasis on water radiolysis, in the nuclear power technology. Radiation chemistry in aqueous system is pointed out to be closely related to the problems such as corrosion of Zircaloy, the formation of insoluble corrosion products or crud, stress corrosion cracking of stainless steel in BWR and the radioactive waste managements. The results of the constant extention rate tests on sensitized 304 stainless steel under irradiation are shown, and the computer calculations were carried out to simulate the model experiments on the release of crud from the corroding surface under irradiation and also the water radiolysis in core of BWR.

Stress Corrosion Cracking of Annealed and Cold Worked Titanium Grade 7 and Alloy 22 in 110 C Concentrated Salt Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

P. Andresen

2000-11-08

Stress corrosion crack growth studies have been performed on annealed and cold worked Titanium Grade 7 and Alloy 22 in 110 C, aerated, concentrated, high pH salt environments characteristic of concentrated ground water. Following a very careful transition from fatigue precracking conditions to SCC conditions, the long term behavior under very stable conditions was monitored using reversing dc potential drop. Titanium Grade 7 exhibited continuous crack growth under both near-static and complete static loading conditions. Alloy 22 exhibited similar growth rates, but was less prone to maintain stable crack growth as conditions approached fully static loading.

Stress corrosion cracking of Ti-8Al-1 Mo-1V in molten salts

NASA Technical Reports Server (NTRS)

Smyrl, W. H.; Blackburn, M. J.

1975-01-01

The stress corrosion cracking (SCC) behavior of Ti-8Al-1 Mo-1V has been studied in several molten salt environments. Extensive data are reported for the alloy in highly pure LiCl-KCl. The influence of the metallurgical heat treatment and texture, and the mechanical microstructure show similarities with aqueous solutions at lower temperature. The fracture path and cracking modes are also similar to that found in other environments. The influence of H2O and H(-) in molten LiCl-KCl lead to the conclusion that hydrogen does not play a major role in crack extension in this environment.

An Investigation into Stress Corrosion Cracking of Dissimilar Metal Welds with 304L Stainless Steel and Alloy 82 in High Temperature Pure Water

NASA Astrophysics Data System (ADS)

Yeh, Tsung-Kuang; Huang, Guan-Ru; Tsai, Chuen-Horng; Wang, Mei-Ya

For a better understanding toward stress corrosion cracking (SCC) in dissimilar metal welds with 304L stainless steel and Alloy 82, the SCC growth behavior in the transition regions of weld joints was investigated via slow strain rate tensile (SSRT) tests in 280 oC pure water with a dissolve oxygen level of 300 ppb. Prior to the SSRT tests, samples with dissimilar metal welds were prepared and underwent various pretreatments, including post-weld heat treatment (PWHT), shot peening, solution annealing, and mechanical grinding. In addition to the SSRT tests, measurements of degree of sensitization and micro-hardness on the transition regions of the metal welds were also conducted. According to the test results, the samples having undergone PWHTs exhibited relatively high degrees of sensitization. Distinct decreases in hardness were observed in the heat-affected zones of the base metals in all samples. Furthermore, the fracture planes of all samples after the SSRT tests were located at the stainless steel sides and were in parallel with the fusion lines. Among the treating conditions investigated in this study, a PWHT would pose a detrimental effect on the samples in the aspects of mechanical property and degree of SCC. Solution annealing would lead to the greatest improvement in ductility and SCC retardation, and shot peening would provide the treated samples with a positive improvement in ductility and corrosion retardation, but not to a great extent.

The effects of hydrogen embrittlement by cathodic protection on the CTOD of buried natural gas pipeline

NASA Astrophysics Data System (ADS)

Kim, Cheol-man; Kim, Woo-sik; Kho, Young-tai

2002-04-01

For the corrosion protection of natural gas transmission pipelines, two methods are used, cathodic protection and a coating technique. In the case of cathodic protection, defects are embrittled by hydrogen occurring at crack tips or surfaces of materials. It is, however, very important to evaluate whether cracks in the embrittled area can grow or not, especially in weld metal. In this work, on the basis of elastic plastic fracture mechanics, we performed CTOD testing under various test conditions, such as potential and current density. The CTOD of the base steel and weld metal showed a strong dependence on the test conditions. The CTOD decreased with increasing cathodic potential and current density. The morphology of the fracture surface showed quasi-cleavage. Cathodic overprotection results in hydrogen embrittlement at the crack tip.

Corrosion resistance of 0Kh18N10T steel in gadolinium nitrate solutions in the liquid regulation of the reactivity of nuclear reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganzha, V.D.; Konoplev, K.A.; Mashchetov, V.P.

1986-03-01

This study was carried out in connection with the preparation of the design for the PIK research reactor. The corrosion resistance of 0Kh18N10T steel in gadolinium nitrate solutions was tested in laboratory, ampule, and loop corrosion tests. At all stages of the tests, the authors investigated the effect produced on the corrosion processes by factors related to the technology of preparation of the equipment (mechanical working of the surfaces, welding, sensitizing, annealing, stressed state of the material, cracks, etc.). Ampule tests were conducted in order to determine the effect produced by reactor radiation and shutdown regimes on the corrosion resistancemore » of the steel. Special ampules made of 0Kh18N10T steel were filled with gadolinium nitrate solutions of various concentrations, sealed, and irradiated for a long period in the core of the VVR-M reactor at a temperature of 20-50 degrees C. The results of the tests are shown. The investigations showed that the corrosion of 0Kh18N10T steel in solutions of gadolinium nitrate is uniform, regardless of the state of the surface, the concentration of gadolinium nitrate, the duration of the tests, the action of the reactor radiation under static and dynamic conditions, and the presence of mechanical stresses.« less

Failure analysis of a Stirling engine heat pipe

NASA Technical Reports Server (NTRS)

Moore, Thomas J.; Cairelli, James E.; Khalili, Kaveh

1989-01-01

Failure analysis was conducted on a heat pipe from a Stirling Engine test rig which was designed to operate at 1073 K. Premature failure had occurred due to localized overheating at the leading edge of the evaporator fin. It was found that a crack had allowed air to enter the fin and react with the sodium coolant. The origin of the crack was found to be located at the inner surface of the Inconel 600 fin where severe intergranular corrosion had taken place.

Evaluation of Alternative Life Assessment Approaches Using P-3 SLAP Test Results

DTIC Science & Technology

2010-06-01

modelling of fatigue crack growth, infrared NDT technologies and fibre optic corrosion detection devices. He joined DSTO in 2007 in the Air Vehicles...10 3.4 Spectra Properties ...the previously conducted (truly ‘blind’) predictions for RAAF usage . DSTO-TR-2418 4 2. Background to DSTO P-3 SLAP Test Interpretation The P

Preparation and corrosion resistance of magnesium phytic acid/hydroxyapatite composite coatings on biodegradable AZ31 magnesium alloy.

PubMed

Zhang, Min; Cai, Shu; Zhang, Feiyang; Xu, Guohua; Wang, Fengwu; Yu, Nian; Wu, Xiaodong

2017-06-01

In this work, a magnesium phytic acid/hydroxyapatite composite coating was successfully prepared on AZ31 magnesium alloy substrate by chemical conversion deposition technology with the aim of improving its corrosion resistance and bioactivity. The influence of hydroxyapatite (HA) content on the microstructure and corrosion resistance of the coatings was investigated. The results showed that with the increase of HA content in phytic acid solution, the cracks on the surface of the coatings gradually reduced, which subsequently improved the corrosion resistance of these coated magnesium alloy. Electrochemical measurements in simulated body fluid (SBF) revealed that the composite coating with 45 wt.% HA addition exhibited superior surface integrity and significantly improved corrosion resistance compared with the single phytic acid conversion coating. The results of the immersion test in SBF showed that the composite coating could provide more effective protection for magnesium alloy substrate than that of the single phytic acid coating and showed good bioactivity. Magnesium phytic acid/hydroxyapatite composite, with the desired bioactivity, can be synthesized through chemical conversion deposition technology as protective coatings for surface modification of the biodegradable magnesium alloy implants. The design idea of the new type of biomaterial is belong to the concept of "third generation biomaterial". Corrosion behavior and bioactivity of coated magnesium alloy are the key issues during implantation. In this study, preparation and corrosion behavior of magnesium phytic acid/hydroxyapatite composite coatings on magnesium alloy were studied. The basic findings and significance of this paper are as follows: 1. A novel environmentally friendly, homogenous and crack-free magnesium phytic acid/hydroxyapatite composite coating was fabricated on AZ31 magnesium alloy via chemical conversion deposition technology with the aim of enhancing its corrosion resistance and bioactivity. The chemical conversion coatings, which are formed through the reaction between the substrate and the environment, have attracted increasing attention owing to the relative low treatment temperature, favorable bonding to substrate and simple implementation process. 2. With the increasing of hydroxyapatite (HA) content, the crack width in the composite coatings and the thickness of the coatings exhibit obviously decreased. The reason is probably that when adding HA into the phytic acid solution, the amount of active hydroxyl groups in the phytic acid are reduced via forming the coordination bond between P-OH groups from phytic acid and P-OH groups from the surface of HA, thus decreasing the coating thickness and hydrogen formation, as well as avoiding coating cracking. 3. By adjusting the HA content to 45 wt.%, a dense and relatively smooth composite coating with ~1.4 μm thickness is obtained on magnesium alloy, and exhibits high corrosion resistance and good bioactivity when compared with the single phytic acid conversion coating.

Maintainability Improvement Through Corrosion Prediction

DTIC Science & Technology

1997-12-01

Aluminum base alloys - Mechanical properties; Lithium- Alloying elements; Crack propagation- Corrosion effects ; Fatigue life - Corrosion... effects on the corrosion fatigue life of 7075-T6 aluminum alloy . Ma,L CORPORATE SOURCE: University of Utah JOURNAL: Dissertation Abstracts International...Diffusion effects ; Hydrogen- Diffusion SECTION HEADINGS: 64 (Corrosion) 52. 715866 87-640094 The Life Prediction for 2024

Grain boundary damage evolution and SCC initiation of cold-worked alloy 690 in simulated PWR primary water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Ziqing; Toloczko, Mychailo B.; Kruska, Karen

Long-term grain boundary (GB) damage evolution and stress corrosion crack initiation in alloy 690 are being investigated by constant load tensile testing in high-temperature, simulated PWR primary water. Six commercial alloy 690 heats are being tested in various cold work conditions loaded at their yield stress. This paper reviews the basic test approach and detailed characterizations performed on selected specimens after an exposure time of ~1 year. Intergranular crack nucleation was observed under constant stress in certain highly cold-worked (CW) alloy 690 heats and was found to be associated with the formation of GB cavities. Somewhat surprisingly, the heats mostmore » susceptible to cavity formation and crack nucleation were thermally treated materials with most uniform coverage of small GB carbides. Microstructure, % cold work and applied stress comparisons are made among the alloy 690 heats to better understand the factors influencing GB cavity formation and crack initiation.« less

Relative stress corrosion susceptibilities of alloys 690 and 600 in simulated boiling water reactor environments

NASA Astrophysics Data System (ADS)

Page, R. A.; McMinn, A.

1986-05-01

The relative susceptibilities of alloys 600 and 690 to intergranular stress corrosion cracking (IGSCC) in pure water and a simulated resin intrusion environment at 288 °C were evaluated. A combination of creviced and noncreviced slow-strain-rate, and precracked fracture mechanics tests were employed in the evaluation. Susceptibility was determined as a function of dissolved oxygen content, degree of sensitization, and crevice condition. The results indicated that alloy 600 was susceptible to various degrees of IGSCC in oxygen containing pure water when creviced, and immune to IGSCC when uncreviced. Alloy 690 was immune to IGSCC under all pure water conditions examined. Alloy 600 and alloy 690 were both susceptible to cracking in the simulated resin intrusion environment. Alloy 690, however, exhibited the greatest resistance to SCC of the two alloys.

Structure and Corrosion Behavior of Arc-Sprayed Zn-Al Coatings on Ductile Iron Substrate

NASA Astrophysics Data System (ADS)

Bonabi, Salar Fatoureh; Ashrafizadeh, Fakhreddin; Sanati, Alireza; Nahvi, Saied Mehran

2018-02-01

In this research, four coatings including pure zinc, pure aluminum, a double-layered coating of zinc and aluminum, and a coating produced by simultaneous deposition of zinc and aluminum were deposited on a cast iron substrate using electric arc-spraying technique. The coatings were characterized by XRD, SEM and EDS map and spot analyses. Adhesion strength of the coatings was evaluated by three-point bending tests, where double-layered coating indicated the lowest bending angle among the specimens, with detection of cracks at the coating-substrate interface. Coatings produced by simultaneous deposition of zinc and aluminum possessed a relatively uniform distribution of both metals. In order to evaluate the corrosion behavior of the coatings, cyclic polarization and salt spray tests were conducted. Accordingly, pure aluminum coating showed susceptibility to pitting corrosion and other coatings underwent uniform corrosion. For double-layered coating, SEM micrographs revealed zinc corrosion products as flaky particles in the pores formed by pitting on the surface, an indication of penetration of corrosion products from the lower layer (zinc) to the top layer (aluminum). All coatings experienced higher negative corrosion potentials than the iron substrate, indicative of their sacrificial behavior.

49 CFR 192.921 - How is the baseline assessment to be conducted?

Code of Federal Regulations, 2011 CFR

2011-10-01

... Transmission Pipeline Integrity Management § 192.921 How is the baseline assessment to be conducted? (a... threats of external corrosion, internal corrosion, and stress corrosion cracking. An operator must conduct...

49 CFR 192.921 - How is the baseline assessment to be conducted?

Code of Federal Regulations, 2012 CFR

2012-10-01

... Transmission Pipeline Integrity Management § 192.921 How is the baseline assessment to be conducted? (a... threats of external corrosion, internal corrosion, and stress corrosion cracking. An operator must conduct...

49 CFR 192.921 - How is the baseline assessment to be conducted?

Code of Federal Regulations, 2013 CFR

2013-10-01

... Transmission Pipeline Integrity Management § 192.921 How is the baseline assessment to be conducted? (a... threats of external corrosion, internal corrosion, and stress corrosion cracking. An operator must conduct...

49 CFR 192.921 - How is the baseline assessment to be conducted?

Code of Federal Regulations, 2014 CFR

2014-10-01

... Transmission Pipeline Integrity Management § 192.921 How is the baseline assessment to be conducted? (a... threats of external corrosion, internal corrosion, and stress corrosion cracking. An operator must conduct...

Determination of the Corrosive Conditions Present within Aircraft Lap-Splice Joints

NASA Technical Reports Server (NTRS)

Lewis, Karen S.; Kelly, Robert G.; Piascik, Robert S.

1999-01-01

The complexity of airframe structure lends itself to damage resulting from crevice corrosion. Fuselage lap-splice joints are a particularly important structural detail in this regard because of the difficulty associated with detection and measurement of corrosion in these occluded regions. The objective of this work is to develop a laboratory corrosion test protocol to identify the chemistry to which lap joints are exposed and to develop a model of the corrosion within the joints. A protocol for collecting and identifying the chemistry of airframe crevice corrosion has been developed. Capillary electrophoresis (CE) is used to identify the ionic species contained in corrosion product samples removed from fuselage lap splice joints. CE analysis has been performed on over sixty corrosion product samples removed from both civilian and military aircraft. Over twenty different ions have been detected. Measurements of pH of wetted corroded surfaces indicated an alkaline occluded solution. After determining the species present and their relative concentrations, the resultant solution was reproduced in bulk and electrochemical tests were performed to determine the corrosion rate. Electrochemical analyses of the behavior of AA2024-T3 in these solutions gave corrosion rates of up to 250 microns per year (10 mpy). Additional tests have determined the relative importance of each of the detected ions in model solutions used for future predictive tests. The statistically significant ions have been used to create a second generation solution. Laboratory studies have also included exposure tests involving artificial lap joints exposed to various simulated bulk and crevice environments. The extent and morphology of the attack in artificial lap joints has been compared to studies of corroded samples from actual aircraft. Other effects, such as temperature and potential, as well as the impact of the environment on fatigue crack growth have also been studied.

75 FR 64633 - Airworthiness Directives; The Boeing Company Model 767-200, -300, and -300F Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-20

... repetitive inspections for fatigue cracking and corrosion of the upper link fuse pin of the nacelle struts... fatigue cracking or corrosion of the upper link fuse pin, which could result in failure of the fuse pin... Model 767-200, -300, and - 300F series airplanes. That AD requires repetitive inspections for fatigue...

Nondestructive Detection of Structural Damage Uniquely Associated with Fatigue

DTIC Science & Technology

1974-07-01

corrosion were not as numerous as cracks caused by fatigue. Stress corrosion cracking occurred mostly at fillet radius, shear pinhole, and the web of...nil i. i^mji^mitm^mm^mmmmmw^mmmtmi>i>i.vi\\ -^^ wix ^w 0) a E re i A c 0) 1- D o ^el /l Current le // T wi th ~ transducer — ’"A

76 FR 10288 - Airworthiness Directives; The Boeing Company Model 767-200, -300, -300F, and -400ER Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-24

... and corrosion to an area within five inches of the fail-safe strap. Revision 2 of this service.... The existing AD currently requires inspections to detect cracking or corrosion of the fail-safe straps... corrective actions. Since we issued that AD, we have received additional reports of cracks in 51 fail-safe...

Development of Innovative Nondestructive Evaluation Technologies for the Inspection of Cracking and Corrosion Under Coatings

NASA Astrophysics Data System (ADS)

Lipetzky, Kirsten G.; Novack, Michele R.; Perez, Ignacio; Davis, William R.

2001-11-01

Three different innovative nondestructive evaluation technologies were developed and evaluated for the ability to detect fatigue cracks and corrosion hidden under painted aluminum panels. The three technologies included real-time ultrasound imaging, thermal imaging, and near-field microwave imaging. With each of these nondestructive inspection methods, subtasks were performed in order to optimize each methodology.

Characterization of the corrosion protection mechanism of cerium-based conversion coatings on high strength aluminum alloys

NASA Astrophysics Data System (ADS)

Pinc, William Ross

The aim of the work presented in this dissertation is to investigate the corrosion protection mechanism of cerium-based conversion coatings (CeCCs) used in the corrosion protection of high strength aluminum alloys. The corrosion resistance of CeCCs involves two general mechanisms; barrier and active. The barrier protection mechanism was influenced by processing parameters, specifically surface preparation, post-treatment, and the use of gelatin. Post-treatment and the addition of gelatin to the coating solution resulted in fewer cracks and transformation of the coating to CePO4, which increased the corrosion resistance by improving the barrier aspect of CeCCs. CeCCs were found to best act as barriers when crack size was limited and CePO4 was present in the coating. CeCCs were found to protect areas of the substrate that were exposed in the coating, indicating that the coatings were more than simple barriers. CeCCs contained large cracks, underneath which subsurface crevices were connected to the surface by the cracks. Despite the observation that no cerium was present in crevices, coatings with crevices exhibited significant corrosion protection. The impedance of post-treated coatings with crevices increased during salt spray exposure. The increase in impedance was associated with the formation of protective oxides / hydroxides; however, crevice-free coatings also exhibited active protection leading to the conclusion that the formation of interfacial layers between the CeCC and the substrate also contributed to the active protection. Based on the overall results of the study, the optimal corrosion protection of CeCCs occurred when processing conditions produced coatings with morphologies and compositions that facilitated both the barrier and active protection mechanisms.

Corrosion Behavior of Steel Reinforcement in Concrete with Recycled Aggregates, Fly Ash and Spent Cracking Catalyst

PubMed Central

Gurdián, Hebé; García-Alcocel, Eva; Baeza-Brotons, Francisco; Garcés, Pedro; Zornoza, Emilio

2014-01-01

The main strategy to reduce the environmental impact of the concrete industry is to reuse the waste materials. This research has considered the combination of cement replacement by industrial by-products, and natural coarse aggregate substitution by recycled aggregate. The aim is to evaluate the behavior of concretes with a reduced impact on the environment by replacing a 50% of cement by industrial by-products (15% of spent fluid catalytic cracking catalyst and 35% of fly ash) and a 100% of natural coarse aggregate by recycled aggregate. The concretes prepared according to these considerations have been tested in terms of mechanical strengths and the protection offered against steel reinforcement corrosion under carbonation attack and chloride-contaminated environments. The proposed concrete combinations reduced the mechanical performance of concretes in terms of elastic modulus, compressive strength, and flexural strength. In addition, an increase in open porosity due to the presence of recycled aggregate was observed, which is coherent with the changes observed in mechanical tests. Regarding corrosion tests, no significant differences were observed in the case of the resistance of these types of concretes under a natural chloride attack. In the case of carbonation attack, although all concretes did not stand the highly aggressive conditions, those concretes with cement replacement behaved worse than Portland cement concretes. PMID:28788613

Effect of an amorphous titania nanotubes coating on the fatigue and corrosion behaviors of the biomedical Ti-6Al-4V and Ti-6Al-7Nb alloys.

PubMed

Campanelli, Leonardo Contri; Bortolan, Carolina Catanio; da Silva, Paulo Sergio Carvalho Pereira; Bolfarini, Claudemiro; Oliveira, Nilson Tadeu Camarinho

2017-01-01

An array of self-organized TiO 2 nanotubes with an amorphous structure was produced on the biomedical Ti-6Al-4V and Ti-6Al-7Nb alloys, and the resulting fatigue and corrosion behaviors were studied. The electrochemical response of the nanotubular oxide surfaces was investigated in Ringer physiological solution through potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The absence of transpassivation in the chloride-containing solution, in addition to the micron-scale values of the passivation current density, indicated the excellent corrosion behavior of the coating and the satisfactory protection against the creation of potential stress concentrators in the surface. Axial fatigue tests were performed in physiological solution on polished and coated conditions, with characterization of the treated surfaces by scanning electron microscopy before and after the tests. The surface modification was not deleterious to the fatigue response of both alloys mainly due to the nano-scale dimension of the nanotubes layer. An estimation based on fracture mechanics revealed that a circumferential crack in the range of 5μm depth would be necessary to affect the fatigue performance, which is far from the thickness of the studied coating, although no cracks were actually observed in the oxide surfaces after the tests. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Effect of Fly Ash on the Corrosion Behaviour of Galvanised Steel Rebarsin Concrete

NASA Astrophysics Data System (ADS)

Tittarelli, Francesca; Mobili, Alessandra; Bellezze, Tiziano

2017-08-01

The effect of fly ash on the corrosion behaviour of galvanised steel rebars in cracked concrete specimens exposed to wet-dry cycles in a chloride solution has been investigated. The obtained results show that the use of fly ash, replacing either cement or aggregate, always improves the corrosion behaviour of galvanised steel reinforcements. In particular, the addition of fly ash, even in the presence of concrete cracks, decreases the corrosion rate monitored in very porous concretes, as those with w/c = 0.80, to values comparable with those obtained in good quality concretes, as those with w/c = 0.45. Therefore, fly ash cancels the negative effect, at least from the corrosion point of view, of a great porosity of the cement matrix.

A film-rupture model of hydrogen-induced, slow crack growth in alpha-beta titanium

NASA Technical Reports Server (NTRS)

Nelson, H. G.

1975-01-01

The appearance of the terrace like fracture morphology of gaseous hydrogen induced crack growth in acicular alpha-beta titanium alloys is discussed as a function of specimen configuration, magnitude of applied stress intensity, test temperature, and hydrogen pressure. Although the overall appearance of the terrace structure remained essentially unchanged, a distinguishable variation is found in the size of the individual terrace steps, and step size is found to be inversely dependent upon the rate of hydrogen induced slow crack growth. Additionally, this inverse relationship is independent of all the variables investigated. These observations are quantitatively discussed in terms of the formation and growth of a thin hydride film along the alpha-beta boundaries and a qualitative model for hydrogen induced slow crack growth is presented, based on the film-rupture model of stress corrosion cracking.

Spatially resolved, in-situ monitoring of crack growth via the coupling current in aluminum alloy 5083

NASA Astrophysics Data System (ADS)

Williams, Krystaufeux D.

The work discussed in this dissertation is an experimental validation of a body of research that was created to model stress corrosion cracking phenomenon for 304 stainless steels in boiling water reactors. This coupled environment fracture model (CEFM) incorporates the natural laws of the conservation of charge and the differential aeration hypothesis to predict the amount of stress corrosion crack growth as a function of many external environmental variables, including potential, stress intensity, solution conductivity, oxidizer concentrations, and various other environmental parameters. Out of this approach came the concept of the coupling current; a local corrosion current that flows from within cracks, crevices, pits, etc... of a metal or alloy to the external surface. Because of the deterministic approach taken in the mentioned research, the coupling current analysis and CEFM model can be applied to the specific problem of SCC in aluminum alloy 5083 (the alloy of interest for this dissertation that is highly sought after today because of its corrosion resistance and high strength to weight ratio). This dissertation research is specifically devoted to the experimental verification of the coupling current, which results from a coupling between the crack's internal and external environments, by spatially resolving them using the scanning vibrating probe (SVP) as a tool. Hence, through the use of a unique fracture mechanics setup, simultaneous mechanical and local electrochemical data may be obtained, in situ..

Study on ductility dip cracking susceptibility in Filler Metal 82 during welding

NASA Astrophysics Data System (ADS)

Chen, Jing-Qing; Lu, Hao; Cui, Wei

2011-06-01

In this paper, Ductility Dip Cracking (DDC) susceptibility in Inconel600 companion Filler Metal 82 (FM82) under different stress states is investigated. Inconel600 is a Ni-Cr-Fe alloy with excellent resistance to general corrosion, localized corrosion, and stress corrosion, which has been widely used in nuclear power plants. However, the companion FM82 has been shown to be susceptible to DDC in welding process. To resolve the problem, this work is mainly focused on evaluating DDC susceptibility in FM82 in welding process. First of all, Strain to Fracture (STF) test is used to achieve the DDC criterion under simple stress state, and the formation mechanism of DDC was explained. Real welding is a process with complex stress state. Later, to get the DDC susceptibility under complex stress state, models about multi-pass welding were built up by means of finite element method. According to numerical simulation results, relationship of deformation and temperature history is achieved. Moreover, susceptible locations and moments could be determined associated with STF results. The simulation results fairly agree with welding experiment from another research.

Linear Cracking in Bridge Decks

DOT National Transportation Integrated Search

2018-03-01

Concrete cracking in bridge decks remains an important issue relative to deck durability. Cracks can allow increased penetration of chlorides, which can result in premature corrosion of the reinforcing steel and subsequent spalling of the concrete de...

Rail base corrosion and cracking prevention

DOT National Transportation Integrated Search

2014-07-01

Rail base corrosion combined with fatigue or damage can significantly reduce rail life. Studies were done to examine the relative contribution of damage, corrosion, and fatigue on rail life. The combined effects can be separated into constituent fact...

Hydroxyapatite-anatase-carbon nanotube nanocomposite coatings fabricated by electrophoretic codeposition for biomedical applications.

PubMed

Zhang, Bokai; Kwok, Chi Tat

2011-10-01

In order to eliminate micro-cracks in the monolithic hydroxyapatite (HA) and composite hydroxyapatite/carbon nanotube (HA/CNT) coatings, novel HA/TiO(2)/CNT nanocomposite coatings on Ti6Al4V were attempted to fabricate by a single-step electrophoretic codeposition process for biomedical applications. The electrophoretically deposited layers with difference contents of HA, TiO(2) (anatase) and CNT nanoparticles were sintered at 800°C for densification with thickness of about 7-10 μm. A dense and crack-free coating was achieved with constituents of 85 wt% HA, 10 wt% TiO(2) and 5 wt% CNT. Open-circuit potential measurements and cyclic potentiodynamic polarization tests were used to investigate the electrochemical corrosion behavior of the coatings in vitro conditions (Hanks' solution at 37°C). The HA/TiO(2)/CNT coatings possess higher corrosion resistance than that of the Ti6Al4V substrate as reflected by nobler open circuit potential and lower corrosion current density. In addition, the surface hardness and adhesion strength of the HA/TiO(2)/CNT coatings are higher than that of the monolithic HA and HA/CNT coatings without compromising their apatite forming ability. The enhanced properties were attributed to the nanostructure of the coatings with the appropriate TiO(2) and CNT contents for eliminating micro-cracks and micro-pores.

Effect of cold work on the stress corrosion cracking behavior of Alloy 690 in supercritical water environment

NASA Astrophysics Data System (ADS)

Chen, Kai; Du, Donghai; Gao, Wenhua; Guo, Xianglong; Zhang, Lefu; Andresen, Peter L.

2018-01-01

The stress corrosion cracking (SCC) behavior of Alloy 690 with 0, 20% and 30% cold work (CW) was studied in supercritical water (SCW) environment with an emphasis on CW and creep on the CGRs (CGR). SCC and creep CGRs increased with %CW, which correlated hardness very well. Microscopic characterization of the crack tip and fracture surface showed obvious cavity-like features, which is clear evidence of creep attack. The creep CGRs in inert gas were comparable to the SCC CGRs in SCW, indicating that creep is a major factor in crack growth. Increasing level of CW was found to increase the creep susceptibility, and high activation energies for creep crack growth were observed between 500 °C and 550 °C.

49 CFR 192.490 - Direct assessment.

Code of Federal Regulations, 2011 CFR

2011-10-01

... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Requirements for Corrosion Control § 192.490 Direct.... Threat Standard 1 External corrosion § 192.925 2 Internal corrosion in pipelines that transport dry gas § 192.927 Stress corrosion cracking § 192.929 1 For lines not subject to subpart O of this part, the...

49 CFR 192.490 - Direct assessment.

Code of Federal Regulations, 2014 CFR

2014-10-01

... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Requirements for Corrosion Control § 192.490 Direct.... Threat Standard 1 External corrosion § 192.925 2 Internal corrosion in pipelines that transport dry gas § 192.927 Stress corrosion cracking § 192.929 1 For lines not subject to subpart O of this part, the...

49 CFR 192.490 - Direct assessment.

Code of Federal Regulations, 2013 CFR

2013-10-01

... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Requirements for Corrosion Control § 192.490 Direct.... Threat Standard 1 External corrosion § 192.925 2 Internal corrosion in pipelines that transport dry gas § 192.927 Stress corrosion cracking § 192.929 1 For lines not subject to subpart O of this part, the...

49 CFR 192.490 - Direct assessment.

Code of Federal Regulations, 2012 CFR

2012-10-01

... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Requirements for Corrosion Control § 192.490 Direct.... Threat Standard 1 External corrosion § 192.925 2 Internal corrosion in pipelines that transport dry gas § 192.927 Stress corrosion cracking § 192.929 1 For lines not subject to subpart O of this part, the...

49 CFR 192.490 - Direct assessment.

Code of Federal Regulations, 2010 CFR

2010-10-01

... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Requirements for Corrosion Control § 192.490 Direct.... Threat Standard 1 External corrosion § 192.925 2 Internal corrosion in pipelines that transport dry gas § 192.927 Stress corrosion cracking § 192.929 1 For lines not subject to subpart O of this part, the...

The stress-corrosion cracking behavior of high-strength aluminum powder metallurgy alloys

NASA Astrophysics Data System (ADS)

Pickens, J. R.; Christodoulou, L.

1987-01-01

The susceptibility to stress-corrosion cracking (SCC) of rapidly solidified (RS) aluminum powder metallurgy (P/M) alloys 7090 and 7091, mechanically alloyed aluminum P/M alloy IN* 9052, and ingot metallurgy (I/M) alloys of similar compositions was compared using bolt-loaded double cantilever beam specimens. In addition, the effects of aging, grain size, grain boundary segregation, pre-exposure embrittlement, and loading mode on the SCC of 7091 were independently assessed. Finally, the data generated were used to elucidate the mechanisms of SCC in the three P/M alloys. The IN 9052 had the lowest SCC susceptibility of all alloys tested in the peak-strength condition, although no SCC was observed in the two RS alloys in the overaged condition. The susceptibility of the RS alloys was greater in the underaged than the peak-aged temper. We detected no significant differences in susceptibility of 7091 with grain sizes varying from 2 to 300 μm. Most of the crack advance during SCC of 7091 was by hydrogen embrittlement (HE). Furthermore, both RS alloys were found to be susceptible to preexposure embrittlement—also indicative of HE. The P/M alloys were less susceptible to SCC than the I/M alloys in all but one test.

Corrosion studies of titanium in borated water for TPX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, D.F.; Pawel, S.J.; DeVan, J.H.

1995-12-31

Corrosion testing was performed to demonstrate the compatibility of the titanium vacuum vessel with borated water. Borated water is proposed to fill the annulus of the double wall vacuum vessel to provide effective radiation shielding. Borating the water with 110 grams of boric acid per liter is sufficient to reduce the nuclear heating in the Toroidal Field Coil set and limit the activation of components external to the vacuum vessel. Constant extension rate tensile (CERT) and electrochemical potentiodynamic tests were performed. Results of the CERT tests confirm that stress corrosion cracking is not significant for Ti-6Al4V or Ti-3AI-2.5V. Welded andmore » unwelded specimens were tested in air and in borated water at 150{degree}C. Strength, elongation, and time to failure were nearly identical for all test conditions, and all the samples exhibited ductile failure. Potentiodynamic tests on Ti-6A1-4V and Ti in borated water as a function of temperature showed low corrosion rates over a wide passive potential range. Further, this passivity appeared stable to anodic potentials substantially greater than those expected from MHD effects.« less

The Role of Deformation and Microchemistry in the Corrosion Processes of Type 304 Stainless Steel in Simulated Pressurized Water Reactor Environments

NASA Astrophysics Data System (ADS)

Fisher, Kevin B.

Degradation of structural components in nuclear environments is a limiting factor in the lifetime of nuclear power plants. Despite decades of research on the topic, there are still aspects of the degradation phenomena that are not well understood, leading to premature failure of components that can be both expensive to repair and potentially dangerous. The current work addresses the role of material deformation on the corrosion phenomena of 304 SS in a simulated nuclear reactor environment by studying the relationship of the material microstructure and microchemistry with the resulting corrosion products using a multiscale analysis approach. The general corrosion phenomenon was studied in relation to the surface deformation of the material, and it was determined that surface deformation not only increases the rate of oxidation, but also has a pronounced impact on the microchemical structure of the oxide film when compared to undeformed material. These findings were applied to understanding the role of deformation in the more complex corrosion phenomena of stress corrosion cracking (SCC) and corrosion fatigue cracking (CFC). In SCC experiments, material deformation in the form of cold work played a synergistic role with unique microchemical features of the materials studied to promote the cracking process under certain environmental and material heat treatment conditions. Despite the fact that the materials studied were low carbon heats of 304L SS thought to be immune to the sensitization and therefore resistant to SCC, elevated boron and delta ferrites in the material were implicated in the SCC susceptibility after heat treatment. On the other hand, low levels of residual deformation played only a minor role in the corrosion processes occurring during CFC experiments over a wide range of rise times. Instead, deformation was suspected to play a larger role in the mechanical cracking response of the material. By studying multiple corrosion processes of 304 SS a greater understanding of the role of deformation and microchemical factors in the related corrosion phenomena has been achieved, and provides evidence that material and component fabrication, in terms of surface and bulk deformation, material microchemistry, and heat treatment must be considered to avoid degradation issues.

Stress Corrosion Cracking of Aluminum Alloys

DTIC Science & Technology

2012-09-10

Hossain and B. J, O’Toole: Stress Corrosion Cracking of Martensitic Stainless Steel for Transmutation Application, Presented at 2003 International...SCC of marternsitic stainless steel by Roy,[12] and learn the annealing effect on SCC of carbon steel by Haruna.[13] The application of slow...observations. In his study on SCC of AISI 304 stainless steel , Roychowdhury[3] detected no apparent SCC in solutions containing 1 ppm thiosulfate and

Effects of H2S/HS- on Stress Corrosion Cracking Behavior of X100 Pipeline Steel Under Simulated Sulfate-Reducing Bacteria Metabolite Conditions

NASA Astrophysics Data System (ADS)

Liu, Q.; Li, Z.; Liu, Z. Y.; Li, X. G.; Wang, S. Q.

2017-04-01

The effect of H2S/HS-, which simulates the main metabolites of sulfate-reducing bacteria (SRB), on the electrochemical and stress corrosion cracking (SCC) behaviors of X100 steel was investigated in a near-neutral solution. The results showed that different H2S/HS- contents mainly affected the cathodic process of X100 electrochemical corrosion. As the concentration of H2S/HS- increased, the corrosion potential was shifted negatively, the corrosion current density was considerably increased, and the corrosion rate was linearly increased. Different rust layers with shifting structures were formed under different conditions and had different effects on electrochemical behaviors. However, sulfide mainly promoted local corrosion processes. With the synergistic effects of stress and H2S/HS-, SCC susceptibility was considerably enhanced. The accelerated process of hydrogen evolution by sulfide was crucial in enhancing SCC processes. In brief, the trace H2S/HS- generated by SRB metabolites played a positive role in promoting SCC.

Rail Base Corrosion and Cracking Prevention: Phase 2

DOT National Transportation Integrated Search

2018-04-09

EWI was engaged by the Federal Railroad Administration to research rail treatments to prevent rail base corrosion in corrosive environments. A coating system was selected in Phase 1 and recommended for field trials. In Phase 2, four railroads sponsor...

Corrosion protection and steel-concrete bond improvement of prestressing strand.

DOT National Transportation Integrated Search

2012-12-01

Corrosion can lead to the premature deterioration and failure of transportation structures. In pre-stressed bridge structures corrosion is more severe, : leading to sudden failures when cracking is induced at pitting sites by tensile or compressive s...

Stress Corrosion Cracking of Basalt/Epoxy Composites under Bending Loading

NASA Astrophysics Data System (ADS)

Shokrieh, Mahmood M.; Memar, Mahdi

2010-04-01

The purpose of this research is to study the stress corrosion behavior of basalt/epoxy composites under bending loading and submerged in 5% sulfuric acid corrosive medium. There are limited numbers of research in durability of fiber reinforced polymer composites. Moreover, studies on basalt fibers and its composites are very limited. In this research, mechanical property degradation of basalt/epoxy composites under bending loading and submerged in acidic corrosive medium is investigated. Three states of stress, equal to 30%, 50% and 70% of the ultimate strength of composites, are applied on samples. High stress states are applied to the samples to accelerate the testing procedure. Mechanical properties degradation consists of bending strength, bending modulus of elasticity and fracture energy of samples are examined. Also, a normalized strength degradation model for stress corrosion condition is presented. Finally, microscopic images of broken cross sections of samples are examined.

77 FR 19567 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-02

... aeroplanes listed in the applicability section of this [EASA] AD. Static, fatigue and corrosion tests were... detect and correct cracked nuts on the fuselage which could result in reduced structural integrity of the... products. The MCAI states: During structural part assembly in Airbus production line, some nuts Part Number...

49 CFR 180.417 - Reporting and record retention requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... other service that may cause stress corrosion cracking, must make a written report containing the... stress relieved after fabrication; (v) Name and address of the person performing the test and the date of... must be furnished to indicate the location of defects detected, such as in weld, heat-affected zone...

49 CFR 180.417 - Reporting and record retention requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... other service that may cause stress corrosion cracking, must make a written report containing the... stress relieved after fabrication; (v) Name and address of the person performing the test and the date of... must be furnished to indicate the location of defects detected, such as in weld, heat-affected zone...

49 CFR 180.417 - Reporting and record retention requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... other service that may cause stress corrosion cracking, must make a written report containing the... stress relieved after fabrication; (v) Name and address of the person performing the test and the date of... must be furnished to indicate the location of defects detected, such as in weld, heat-affected zone...

Environment enhanced fatigue crack propagation in metals: Inputs to fracture mechanics life prediction models

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Kim, Sang-Shik

1993-01-01

This report is a critical review of both environment-enhanced fatigue crack propagation data and the predictive capabilities of crack growth rate models. This information provides the necessary foundation for incorporating environmental effects in NASA FLAGRO and will better enable predictions of aerospace component fatigue lives. The review presents extensive literature data on 'stress corrosion cracking and corrosion fatigue.' The linear elastic fracture mechanics approach, based on stress intensity range (Delta(K)) similitude with microscopic crack propagation threshold and growth rates, provides a basis for these data. Results are presented showing enhanced growth rates for gases (viz., H2 and H2O) and electrolytes (e.g. NaCl and H2O) in aerospace alloys including: C-Mn and heat treated alloy steels, aluminum alloys, nickel-based superalloys, and titanium alloys. Environment causes purely time-dependent accelerated fatigue crack growth above the monotonic load cracking threshold (KIEAC) and promotes cycle-time dependent cracking below (KIEAC). These phenomenon are discussed in terms of hydrogen embrittlement, dissolution, and film rupture crack tip damage mechanisms.

An automated tool joint inspection device for the drill string

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moyer, M.C.; Dale, B.A.; Kusenberger, F.N.

1983-02-01

This paper discusses the development of an automated tool joint inspection device (i.e., the Fatigue Crack Detector), which is capable of detecting defects in the threaded region of drill pipe and drill collars. On the basis of inspection tests conducted at a research test facility and at drilling rig sites, this device is capable of detecting both simulated defects (saw slots and drilled holes) and service-induced defects, such as fatigue cracks, pin stretch (plastic deformation), mashed threads, and corrosion pitting. The system employs an electromagnetic flux-leakage principle and has several advantages over the conventional method of magnetic particle inspection.

Penetrative Internal Oxidation from Alloy 690 Surfaces and Stress Corrosion Crack Walls during Exposure to PWR Primary Water

NASA Astrophysics Data System (ADS)

Olszta, Matthew J.; Schreiber, Daniel K.; Thomas, Larry E.; Bruemmer, Stephen M.

Analytical electron microscopy and three-dimensional atom probe tomography (ATP) examinations of surface and near-surface oxidation have been performed on Ni-30%Cr alloy 690 materials after exposure to high-temperature, simulated PWR primary water. The oxidation nanostructures have been characterized at crack walls after stress-corrosion crack growth tests and at polished surfaces of unstressed specimens for the same alloys. Localized oxidation was discovered for both crack walls and surfaces as continuous filaments (typically <10 nm in diameter) extending from the water interface into the alloy 690 matrix reaching depths of 500 nm. These filaments consisted of discrete, plate-shaped Cr2O3 particles surrounded by a distribution of nanocrystalline, rock-salt (Ni-Cr-Fe) oxide. The oxide-containing filament depth was found to increase with exposure time and, at longer times, the filaments became very dense at the surface leaving only isolated islands of metal. Individual dislocations were oxidized in non-deformed materials, while the oxidation path appeared to be along more complex dislocation substructures in heavily deformed materials. This paper will highlight the use of high resolution scanning and transmission electron microscopy in combination with APT to better elucidate the microstructure and microchemistry of the filamentary oxidation.

Corrosion and fatigue of surgical implants

NASA Technical Reports Server (NTRS)

Lisagor, W. B.

1975-01-01

Implants for the treatment of femoral fractures, mechanisms leading to the failure or degradation of such structures, and current perspectives on surgical implants are discussed. Under the first heading, general usage, materials and procedures, environmental conditions, and laboratory analyses of implants after service are considered. Corrosion, crevice corrosion, stress corrosion cracking, intergranular corrosion, pitting corrosion, fatigue, and corrosion fatigue are the principal degradation mechanisms described. The need for improvement in the reliability of implants is emphasized.

Contributions of stress corrosion and cyclic fatigue to subcritical crack growth in a dental glass-ceramic.

PubMed

Joshi, Gaurav V; Duan, Yuanyuan; Della Bona, Alvaro; Hill, Thomas J; St John, Kenneth; Griggs, Jason A

2014-08-01

The objective of this study was to test the following hypotheses: (1) both cyclic degradation and stress-corrosion mechanisms result in subcritical crack growth (SCG) in a fluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent) and (2) there is an interactive effect of stress corrosion and cyclic fatigue to accelerate subcritical crack growth. Rectangular beam specimens were fabricated using the lost-wax process. Two groups of specimens (N=30/group) with polished (15μm) or air-abraded surface were tested under rapid monotonic loading. Additional polished specimens were subjected to cyclic loading at two frequencies, 2Hz (N=44) and 10Hz (N=36), and at various stress amplitudes. All tests were performed using a fully articulated four-point flexure fixture in deionized water at 37°C. The SCG parameters were determined using the ratio of inert strength Weibull modulus to lifetime Weibull modulus. A general log-linear model was fit to the fatigue lifetime data including time to failure, frequency, peak stress, and the product of frequency and logarithm of stress in ALTA PRO software. SCG parameters determined were n=21.7 and A=4.99×10(-5) for 2Hz, and n=19.1 and A=7.39×10(-6) for 10Hz. After fitting the general log-linear model to cyclic fatigue data, the coefficients of the frequency term (α1), the stress term (α2), and the interaction term (α3) had estimates and 95% confidence intervals of α1=-3.16 (-15.1, 6.30), α2=-21.2 (-34.9, -9.73), and α3=0.820 (-1.59, 4.02). Only α2 was significantly different from zero. (1) Cyclic fatigue does not have a significant effect on SCG in the fluorapatite glass-ceramic evaluated and (2) there was no interactive effect between cyclic degradation and stress corrosion for this material. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

dK/da effects on the SCC growth rates of nickel base alloys in high-temperature water

NASA Astrophysics Data System (ADS)

Chen, Kai; Wang, Jiamei; Du, Donghai; Andresen, Peter L.; Zhang, Lefu

2018-05-01

The effect of dK/da on crack growth behavior of nickel base alloys has been studied by conducting stress corrosion cracking tests under positive and negative dK/da loading conditions on Alloys 690, 600 and X-750 in high temperature water. Results indicate that positive dK/da accelerates the SCC growth rates, and the accelerating effect increases with dK/da and the initial CGR. The FRI model was found to underestimate the dK/da effect by ∼100X, especially for strain hardening materials, and this underscores the need for improved insight and models for crack tip strain rate. The effect of crack tip strain rate and dK/dt in particular can explain the dK/da accelerating effect.

78 FR 1726 - Airworthiness Directives; Burkhart GROB Luft- und Raumfahrt GmbH Sailplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-09

... purposes of this AD, we define slight corrosion as corrosion you can remove with metal wool and that has no visible pitting in the base metal. If you cannot remove the corrosion with metal wool or if there is visible pitting in the base metal, we define it as heavy corrosion. (3) If any cracks or heavy corrosion...

Design Criteria for Controlling Stress Corrosion Cracking

NASA Technical Reports Server (NTRS)

Franklin, D. B.

1987-01-01

This document sets forth the criteria to be used in the selection of materials for space vehicles and associated equipment and facilities so that failure resulting from stress corrosion will be prevented. The requirements established herein apply to all metallic components proposed for use in space vehicles and other flight hardware, ground support equipment, and facilities for testing. These requirements are applicable not only to items designed and fabricated by MSFC (Marshall Space Flight Center) and its prime contractors, but also to items supplied to the prime contractor by subcontractors and vendors.

Sealing of Cracks on Florida Bridge Decks with Steel Girders [Summary

DOT National Transportation Integrated Search

2012-01-01

Transverse cracking is common in concrete bridge decks, degrading both aesthetic and structural properties of the bridge. Cracks expose reinforcing steel and supporting steel to corrosive agents, such as water or chemicals, which shorten deck service...

Measurements and mechanisms of localized aqueous corrosion in aluminum-lithium alloys

NASA Technical Reports Server (NTRS)

Buchheit, Rudolph G., Jr.; Stoner, Glenn E.

1990-01-01

Like most heat treatable aluminum alloys, localized corrosion and stress corrosion of Al-Li-Cu alloys is strongly dependent on the nature and distribution of second phase particles. To develop a mechanistic understanding of the role of localized corrosion in the stress corrosion process, bulk samples of T(sub 1) (Al2CuLi) and a range of Al-Cu-Fe impurity phases were prepared for electrochemical experiments. Potentiodynamic polarization and galvanic couple experiments were performed in standard 0.6 M NaCl and in simulated crevice solutions to assess corrosion behavior of these particles with respect to the alpha-Al matrix. A comparison of time to failure versus applied potential using a constant load, smooth bar SCC test technique in Cl(-), Cl(-)/CrO4(2-), and Cl(-)/CO3(2-) environments shows that rapid failures are to be expected when applied potentials are more positive than the breakaway potential (E sub br) of T(sub 1) (crack tip) but less than E(sub br) of alpha-Al (crack walls). It is shown that this criterion is not satisfied in aerated Cl(-) solutions. Accordingly, SCC resistance is good. This criterion is satisfied, however, in an alkaline isolated fissure exposed to a CO2 containing atmosphere. Rapid failure induced by these fissures was recently termed preexposure embrittlement. Anodic polarization shows that the corrosion behavior of T(sub 1) is relatively unaffected in alkaline CO3(2-) environments but the alpha-Al phase is rapidly passivated. X ray diffraction of crevice walls from artificial crevices suggests that passivation of alpha-Al occurs as hydrotalcite-type compound (LiAl2(OH)6)2(+) - CO3(2-) - nH2O.

Beryllium fluoride film protects beryllium against corrosion

NASA Technical Reports Server (NTRS)

O donnell, P. M.; Odonnell, P. M.

1967-01-01

Film of beryllium fluoride protects beryllium against corrosion and stress corrosion cracking in water containing chloride ion concentrations. The film is formed by exposing the beryllium to fluorine gas at 535 degrees C or higher and makes beryllium suitable for space applications.

Shear capacity assessment of corrosion-damaged reinforced concrete beams : final report.

DOT National Transportation Integrated Search

2003-12-01

This study investigated how the shear capacity of reinforced concrete bridge beams is affected by corrosion damage to the shear stirrups. It described the changes that occur in shear capacity and concrete cracking as shear stirrup corrosion progresse...

Influence of Localized Plasticity on IASCC Sensitivity of Austenitic Stainless Steels under PWR Primary Water

NASA Astrophysics Data System (ADS)

Cissé, Sarata; Tanguy, Benoit; Laffont, Lydia; Lafont, Marie-Christine; Guerre, Catherine; Andrieu, Eric

The sensibility of precipitation-strengthened A286 austenitic stainless steel to Stress Corrosion Cracking (SCC) is studied by means of Slow Strain Rate Tests (SSRT). First, alloy cold working by Low Cycle Fatigue (LCF) is investigated. Fatigue tests under plastic strain control are performed at different strain levels (Δ ɛp/2=0.2%, 0.5% and 0.8%) in order to establish correlation between stress softening and deformation microstructure resulting from LCF tests. Deformed microstructures have been identified through TEM investigations. Three states of cyclic behaviour for precipitation-strengthened A286 have been identified: hardening, cyclic softening and finally saturation of softening. It is shown that the A286 alloy cyclic softening is due to microstructural features such as defects — free deformation bands resulting from dislocations motion along family plans <111>, that swept defects or γ' precipitates and lead to deformation localization. In order to quantify effects of plastic localized deformation on intergranular stress corrosion cracking (IGSCC) of the A286 alloy in PWR primary water, slow strain rate tests are conducted. For each cycling conditions, two specimens at a similar stress level are tested: the first containing free precipitate deformation bands, the other not significant of a localized deformation state. SSRT tests are still in progress.

Below-Ambient and Cryogenic Thermal Testing

NASA Technical Reports Server (NTRS)

Fesmire, James E.

2016-01-01

Thermal insulation systems operating in below-ambient temperature conditions are inherently susceptible to moisture intrusion and vapor drive toward the cold side. The subsequent effects may include condensation, icing, cracking, corrosion, and other problems. Methods and apparatus for real-world thermal performance testing of below-ambient systems have been developed based on cryogenic boiloff calorimetry. New ASTM International standards on cryogenic testing and their extension to future standards for below-ambient testing of pipe insulation are reviewed.

Corrosion behavior of mesoporous bioglass-ceramic coated magnesium alloy under applied forces.

PubMed

Zhang, Feiyang; Cai, Shu; Xu, Guohua; Shen, Sibo; Li, Yan; Zhang, Min; Wu, Xiaodong

2016-03-01

In order to research the corrosion behavior of bioglass-ceramic coated magnesium alloys under applied forces, mesoporous 45S5 bioactive glass-ceramic (45S5 MBGC) coatings were successfully prepared on AZ31 substrates using a sol-gel dip-coating technique followed by a heat treatment at the temperature of 400°C. In this work, corrosion behavior of the coated samples under applied forces was characterized by electrochemical tests and immersion tests in simulated body fluid. Results showed that the glass-ceramic coatings lost the protective effects to the magnesium substrate in a short time when the applied compressive stress was greater than 25MPa, and no crystallized apatite was formed on the surface due to the high Mg(2+) releasing and the peeling off of the coatings. Whereas, under low applied forces, apatite deposition and crystallization on the coating surface repaired cracks to some extent, thus improving the corrosion resistance of the coated magnesium during the long-term immersion period. Copyright © 2015 Elsevier Ltd. All rights reserved.

Review of recent developments in the field of magnesium corrosion: Recent developments in Mg corrosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atrens, Andrej; Song, Guang -Ling; Liu, Ming

2015-01-07

This paper provides a review of recent developments in the field of Mg corrosion and puts those into context. This includes considerations of corrosion manifestations, material influences, surface treatment, anodization, coatings, inhibition, biodegradable medical applications, stress corrosion cracking, flammability, corrosion mechanisms for HP Mg, critical evaluation of corrosion mechanisms, and concluding remarks. There has been much research recently, and much research continues in this area. In conclusion, this is expected to produce significantly better, more-corrosion-resistant Mg alloys.

Hot corrosion of ceramic engine materials

NASA Technical Reports Server (NTRS)

Fox, Dennis S.; Jacobson, Nathan S.; Smialek, James L.

1988-01-01

A number of commercially available SiC and Si3N4 materials were exposed to 1000 C in a high velocity, pressurized burner rig as a simulation of a turbine engine environment. Sodium impurities added to the burner flame resulted in molten Na2SO4 deposition, attack of the SiC and Si4N4 and formation of substantial Na2O-x(SiO2) corrosion product. Room temperature strength of the materials decreased. This was a result of the formation of corrosion pits in SiC, and grain boundary dissolution and pitting in Si3N4. Corrosion regimes for such Si-based ceramics have been predicted using thermodynamics and verified in rig tests of SiO2 coupons. Protective mullite coatings are being investigated as a solution to the corrosion problem for SiC and Si3N4. Limited corrosion occurred to cordierite (Mg2Al4Si5O18) but some cracking of the substrate occurred.

Anti-corrosion mechanism of epoxy-resin and different content Fe2O3 coatings on magnesium alloy

NASA Astrophysics Data System (ADS)

Jin, Tao; Kong, Fan-mei; Bai, Rui-qin; Zhang, Ru-liang

2016-12-01

In this study, anti-corrosion coatings were prepared and coated successfully on magnesium alloy substrates by mixing nanopowders, solvent, curing agent with epoxy resin. The effect of the amount of iron trioxide (Fe2O3) on the adhesion strength and corrosion resistance on magnesium alloy was investigated with standard protocols, and electrochemical measurements were also made in 3.5 wt.% NaCl solutions. The surface morphology and corrosion mechanism after corrosion tests was characterized using FESEM analysis. Nanoparticles in matrix acted as filler, and interstitial cross-linked spaces and other coating artifacts regions (micro cracks and voids) would all affect the anti-corrosion properties of coating. The results showed the proper powder content not only provided adhesion strength to these coatings but also improved obviously their anticorrosion. Hydrogen bound to the amine nitrogen (1N) could take part in the curing process rather than hydrogen of the amide site due to the smaller Δ G and the more stable configuration.

Studies on microstructure, mechanical and corrosion properties of high nitrogen stainless steel shielded metal arc welds

NASA Astrophysics Data System (ADS)

Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

The present work is aimed at studying the microstructure, mechanical and corrosion properties of high nitrogen stainless steel shielded metal arc (SMA) welds made with Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microstructures of the welds were characterized using optical microscopy (OM), field emission scanning electron microscopy (FESEM) and electron back scattered diffraction (EBSD) mainly to determine the morphology, phase analysis, grain size and orientation image mapping. Hardness, tensile and ductility bend tests were carried out to determine mechanical properties. Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance using a GillAC basic electrochemical system. Constant load type testing was carried out to study stress corrosion cracking (SCC) behaviour of welds. The investigation results shown that the selected Cr–Mn–N type electrode resulted in favourable microstructure and completely solidified as single phase coarse austenite. Mechanical properties of SMA welds are found to be inferior when compared to that of base metal and is due to coarse and dendritic structure.

How do titanium and Ti6Al4V corrode in fluoridated medium as found in the oral cavity? An in vitro study.

PubMed

Souza, Júlio C M; Barbosa, Sandra L; Ariza, Edith A; Henriques, Mariana; Teughels, Wim; Ponthiaux, Pierre; Celis, Jean-Pierre; Rocha, Luis A

2015-02-01

The purpose of this work was to evaluate the corrosion of commercially pure (CP) titanium and Ti6Al4V in vitro at different F(-) concentrations regularly found in the oral cavity by using different electrochemical tests and surface analysis techniques. electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and potentiodynamic polarization tests were associated to advanced characterization techniques such as SEM, EDS, AFM, ICP-MS and XPS. OCP tests revealed a higher reactivity of both CP titanium and Ti6Al4V at 12,300 ppm F(-) concentration than that recorded at 227 ppm F(-). Also, a significant decrease of the corrosion resistance of both materials was noticed by EIS in fluoride solutions. Material loss caused by corrosion was noticed on titanium surfaces by SEM and AFM in the presence of high F(-) concentration. CP titanium degraded by pitting corrosion while Ti6Al4V suffered from general corrosion showing micro-cracks on surface. Furthermore, a high release of metallic ions from the test samples after immersion at high F(-) concentrations was detected by ICP-MS, that can be potentially toxic to oral tissues. Copyright © 2014 Elsevier B.V. All rights reserved.

Environmental effects on aluminum fracture

NASA Technical Reports Server (NTRS)

Schwartzberg, F. R.; Shepic, J. A.

1976-01-01

The sustained load stress corrosion cracking (SCC) threshold for aluminum alloy 214 was determined using smooth (sigma sub TH) and precracked (K sub ISCC) specimens, and cyclic load growth behavior in 3.5% NaCl salt solution was studied. The relationship between K sub ISCC and sigma sub TH was also studied. The work showed that 2124-T851 aluminum alloy in plate gage has a moderately high resistance to stress corrosion attack. Experimental results showed that no SCC occurred in the longitudinal and long transverse directions in any of the tests. Some SCC was found by smooth tests in the short transverse direction, and the data were confirmed by two test methods-sigma sub TH = 275 MN/sq m (40 ksi). No SCC was found from compact specimen tests in any direction: surface flaw and center notch specimens evaluated in the short transverse direction exhibited SCC. The data indicate that stress corrosion behavior is defect, size, and stress dependent, but not entirely in accordance with a stress intensity controlled mechanism.

Mitigation strategies for early-age shrinkage cracking in bridge decks.

DOT National Transportation Integrated Search

2010-04-01

Early-age shrinkage cracking has been observed in many concrete bridge decks in Washington State and elsewhere around the U.S. The cracking increases the effects of freeze-thaw damage, spalling, and corrosion of steel reinforcement, thus resulting in...

Characterization of Cracking and Crack Growth Properties of the C5A Aircraft Tie-Box Forging

NASA Technical Reports Server (NTRS)

Piascik, Robert S.; Smith, Stephen W.; Newman, John A.; Willard, Scott A.

2003-01-01

Detailed destructive examinations were conducted to characterize the integrity and material properties of two aluminum alloy (7075-T6) horizontal stabilizer tie box forgings removed.from US. Air Force C5A and C5B transport aircraft. The C5B tie box forging was,found to contain no evidence of cracking. Thirteen cracks were found in the CSA,forging. All but one of the cracks observed in the C5A component were located along the top cap region (one crack was located in the bottom cap region). The cracks in the C5A component initiated at fastener holes and propagated along a highly tunneled intergranular crack path. The tunneled crack growth configuration is a likelv result of surface compressive stress produced during peening of the .forging suijace. The tie box forging ,fatigue crack growth, fracture and stress corrosion cracking (SCC) properties were characterized. Reported herein are the results of laboratory air ,fatigue crack growth tests and 95% relative humidity SCC tests conducted using specimens machined from the C5A ,forging. SCC test results revealed that the C5A ,forging material was susceptible to intergranular environmental assisted cracking: the C5A forging material exhibited a SCC crack-tip stress-intensity factor threshold of less than 6 MPadn. Fracture toughness tests revealed that the C5A forging material exhibited a fracture toughness that was 25% less than the C5B forging. The C5A forging exhibited rapid laboratory air fatigue crack growth rates having a threshold crack-tip stress-intensity factor range of less than 0.8 MPa sup m. Detailed fractographic examinations revealed that the ,fatigue crack intergranular growth crack path was similar to the cracking observed in the C5A tie box forging. Because both fatigue crack propagation and SCC exhibit similar intergranular crack path behavior, the damage mechanism resulting in multi-site cracking of tie box forgings cannot be determined unless local cyclic stresses can be quantified.

Materials for the pulp and paper industry. Section 1: Development of materials for black liquor recovery boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keiser, J.R.; Hubbard, C.R.; Payzant, E.A.

1997-04-01

Black liquor recovery boilers are essential components of kraft pulp and paper mills because they are a critical element of the system used to recover the pulping chemicals required in the kraft pulping process. In addition, the steam produced in these boilers is used to generate a significant portion of the electrical power used in the mill. Recovery boilers require the largest capital investment of any individual component of a paper mill, and these boilers are a major source of material problems in a mill. The walls and floors of these boilers are constructed of tube panels that circulate highmore » pressure water. Molten salts (smelt) accumulate on the floor of recovery boilers, and leakage of water into the boiler can result in a violent explosion when the leaked water instantly vaporizes upon contacting the molten smelt. Because corrosion of the conventionally-used carbon steel tubing was found to be excessive in the lower section of recovery boilers, use of stainless steel/carbon steel co-extruded tubing was adopted for boiler walls to lessen corrosion and reduce the likelihood of smelt/water explosions. Eventually, this co-extruded or composite (as it is known in the industry) tubing was selected for use as a portion or all of the floor of recovery boilers, particularly those operating at pressures > 6.2 MPa (900 psi), because of the corrosion problems encountered in carbon steel floor tubes. Since neither the cause of the cracking nor an effective solution has been identified, this program was established to develop a thorough understanding of the degradation that occurs in the composite tubing used for walls and floors. This is being accomplished through a program that includes collection and review of technical reports, examination of unexposed and cracked tubes from boiler floors, computer modeling to predict residual stresses under operating conditions, and operation of laboratory tests to study corrosion, stress corrosion cracking, and thermal fatigue.« less

Corrosion protection of prestressing strand in transportation structures and strand-concrete bond improvement.

DOT National Transportation Integrated Search

2012-12-01

Corrosion can lead to the premature deterioration and failure of transportation structures. In pre-stressed bridge structures corrosion is more severe, : leading to sudden failures when cracking is induced at pitting sites by tensile or compressive s...

Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Form Domes

NASA Technical Reports Server (NTRS)

Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

2010-01-01

Damage tolerance testing development was required to help qualify a new spin forming dome fabrication process for the Ares 1 program at Marshall Space Flight Center (MSFC). One challenge of the testing was due to the compound curvature of the dome. The testing was developed on a sub-scale dome with a diameter of approximately 40 inches. The simulated service testing performed was based on the EQTP1102 Rev L 2195 Aluminum Lot Acceptance Simulated Service Test and Analysis Procedure generated by Lockheed Martin for the Space Shuttle External Fuel Tank. This testing is performed on a specimen with an induced flaw of elliptical shape generated by Electrical Discharge Machining (EDM) and subsequent fatigue cycling for crack propagation to a predetermined length and depth. The specimen is then loaded in tension at a constant rate of displacement at room temperature until fracture occurs while recording load and strain. An identical specimen with a similar flaw is then proof tested at room temperature to imminent failure based on the critical offset strain achieved by the previous fracture test. If the specimen survives the proof, it is then subjected to cryogenic cycling with loads that are a percentage of the proof load performed at room temperature. If all cryogenic cycles are successful, the specimen is loaded in tension to failure at the end of the test. This standard was generated for flat plate, so a method of translating this to a specimen of compound curvature was required. This was accomplished by fabricating a fixture that maintained the curvature of the specimen rigidly with the exception of approximately one-half inch in the center of the specimen containing the induced flaw. This in conjunction with placing the center of the specimen in the center of the load train allowed for successful testing with a minimal amount of bending introduced into the system. Stress corrosion cracking (SCC) tests were performed using the typical double beam assembly and with 4-point loaded specimens under alternate immersion conditions in a 3.5% NaCl environment for 90 days. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K1SCC) of Al-Li 2195 which to our knowledge has not been determined previously. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication.

Cluster analysis of stress corrosion mechanisms for steel wires used in bridge cables through acoustic emission particle swarm optimization.

PubMed

Li, Dongsheng; Yang, Wei; Zhang, Wenyao

2017-05-01

Stress corrosion is the major failure type of bridge cable damage. The acoustic emission (AE) technique was applied to monitor the stress corrosion process of steel wires used in bridge cable structures. The damage evolution of stress corrosion in bridge cables was obtained according to the AE characteristic parameter figure. A particle swarm optimization cluster method was developed to determine the relationship between the AE signal and stress corrosion mechanisms. Results indicate that the main AE sources of stress corrosion in bridge cables included four types: passive film breakdown and detachment of the corrosion product, crack initiation, crack extension, and cable fracture. By analyzing different types of clustering data, the mean value of each damage pattern's AE characteristic parameters was determined. Different corrosion damage source AE waveforms and the peak frequency were extracted. AE particle swarm optimization cluster analysis based on principal component analysis was also proposed. This method can completely distinguish the four types of damage sources and simplifies the determination of the evolution process of corrosion damage and broken wire signals. Copyright © 2017. Published by Elsevier B.V.

Terahertz NDE for Under Paint Corrosion Detection and Evaluation

NASA Technical Reports Server (NTRS)

Anastasi, Robert F.; Madaras, Eric I.

2005-01-01

Corrosion under paint is not visible until it has caused paint to blister, crack, or chip. If corrosion is allowed to continue then structural problems may develop. Identifying corrosion before it becomes visible would minimize repairs and costs and potential structural problems. Terahertz NDE imaging under paint for corrosion is being examined as a method to inspect for corrosion by examining the terahertz response to paint thickness and to surface roughness.

The influence of manufacturing processes on the microstructure, grain boundary characteristics and SCC behavior of Alloy 690 steam generator tubing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarver, J.M.; Doherty, P.E.; Doyle, D.M.

1995-12-31

Thermally treated Alloy 690 is the tubing material of choice for replacement steam generators in the United States. Throughout the world, it is manufactured using different melting and thermomechanical processing methods. The influence of different processing steps on the intergranular stress corrosion cracking (IGSCC) behavior of Alloy 690 has not been thoroughly evaluated. Evaluations were performed on Alloy 690 steam generator tubing produced using several different melting practices and thermomechanical processing procedures. The evaluations included extensive microstructural examinations as well as constant extension rate (CERT) tests. The CERT test results indicated that the thermally treated Alloy 690 tubing which wasmore » subjected to higher annealing temperatures displayed the highest degree of resistance to stress corrosion cracking (SCC). Examination of the microstructures indicated that the microstructural changes which are produced by increased annealing temperatures are subtle. In an attempt to further elucidate and quantify the effect of manufacturing processes on corrosion behavior, grain boundary character distribution (GBCD) measurements were performed on the same materials which were CERT tested. Analysis of GBCDs of the samples used in this study indicate that Alloy 690 exhibits a significantly larger fraction of special boundaries as compared to Alloy 600 and Alloy 800, regardless of the processing history of the tubing. Preliminary results indicate that a correlation may exist between processing method, GBCD`s and degree of IGSCC exhibited by the thermally treated samples examined in this study.« less

76 FR 18454 - Airworthiness Directives; Burl A. Rogers (Type Certificate Previously Held by William Brad...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-04

... cracks and/or corrosion and installing inspection access panels. This AD would also require replacing the wing spar cap angles if moderate or severe corrosion is found and applying corrosion inhibitor. This proposed AD was prompted by reports of intergranular exfoliation and corrosion of the upper and/or lower...

Application of electroless Ni-P coating on magnesium alloy via CrO3/HF free titanate pretreatment

NASA Astrophysics Data System (ADS)

Rajabalizadeh, Z.; Seifzadeh, D.

2017-11-01

The titanate conversion coating was applied as CrO3/HF free pretreatment for the electroless Ni-P plating on AM60B magnesium alloy. The microscopic images revealed that the alloy surface was completely covered by a cracked conversion film after titanate pretreatment which was mainly composed of Mg(OH)2/MgO, MgF2, TiO2, SiO2, and Al2O3/Al(OH)3. The microscopic images also revealed that numerous Ni nucleation centers were formed over the titanate film after short electroless plating times. The nucleation centers were created not only on the cracked area but also over the whole pretreated surface due to the catalytic action of the titanate film. Also, uniform, dense, and defect-free Ni-P coating with fine structure was achieved after 3 h plating. The Ni-P coating showed mixed crystalline-amorphous structure due to its moderate phosphorus content. The results of two traditional corrosion monitoring methods indicated that the Ni-P coating significantly increases the corrosion resistance of the magnesium alloy. Moreover, Electrochemical Noise (EN) method was used as a non-polarized technique to study the corrosion behavior of the electroless coating at different immersion times. The results of the EN tests were clearly showed the localized nature of the corrosion process. Micro-hardness value of the magnesium alloy was remarkably enhanced after the electroless plating. Finally, suitable adhesion between the Ni-P coating and the magnesium alloy substrate was confirmed by thermal shock and pull-off-adhesion tests.

Effect of Thermomechanical Treatment on the Environmentally Induced Cracking Behavior of AA7075 Alloy

NASA Astrophysics Data System (ADS)

Ghosh, Rahul; Venugopal, A.; Sankaravelayudham, P.; Panda, Rajiv; Sharma, S. C.; George, Koshy M.; Raja, V. S.

2015-02-01

The influence of thermomechanical treatment on the stress corrosion cracking behavior of AA7075 aluminum alloy forgings was examined in 3.5% NaCl solution by varying the extent of thermomechanical working imparted to each of the conditions. The results show that inadequate working during billet processing resulted in inferior corrosion and mechanical properties. However, more working with intermediate pre-heating stages also led to precipitation of coarse particles resulting in lowering of mechanical properties marginally and a significant reduction in the general/pitting corrosion resistance. The results obtained in the present study indicate that optimum working with controlled pre-heating levels is needed during forging to achieve the desired properties. It is also demonstrated that AA7075 in the over aged condition does not show any environmental cracking susceptibility in spite of the microstructural variations in terms of size and volume fraction of the precipitates. However, the above microstructural variations definitely affected the pitting corrosion and mechanical properties significantly and hence a strict control over the working and pre-heating stages during billet processing is suggested.

A Study on Fretting Behavior in Room Temperature for Inconel Alloy 690

NASA Astrophysics Data System (ADS)

Kwon, Jae Do; Chai, Young Suck; Bae, Yong Tak; Choi, Sung Jong

The initial crack under fretting condition occurs at lower stress amplitude and lower cycles of cyclic loading than that under plain fatigue condition. The fretting damage, for example, can be observed in fossil and nuclear power plant, aircraft, automobile and petroleum chemical plants etc. INCONEL alloy 690 is a high-chromium nickel alloy having excellent resistance to many corrosive aqueous media and high-temperature atmospheres. This alloy is used extensively in the industries of nuclear power, chemicals, heat-treatment and electronics. In this paper, the effect of fretting damage on fatigue behavior for INCONEL alloy 690 was studied. Also, various kinds of tests on mechanical properties such as hardness, tension and plain fatigue tests are performed. Fretting fatigue tests were carried out with flat-flat contact configuration using a bridge type contact pad and plate type specimen. Through these experiments, it is found that the fretting fatigue strength decreased about 43% compared to the plain fatigue strength. In fretting fatigue, the wear debris is observed on the contact surface, and the oblique micro-cracks are initiated at an earlier stage. These results can be used as the basic data in a structural integrity evaluation of heat and corrosion resistant alloy considering fretting damages.

Micromechanisms of Crack Growth in Ceramics and Glasses in Corrosive Environments.

DTIC Science & Technology

1980-05-01

Resistance Mecanique du Verre et les Moyens de l’Amelioree, Union Scientifique Continentale du Verre , Charleroix, Belgium, (1962). 8. B. A. Proctor, I...exhibit similar types of delayed failure curves. Failure occurs most rapidly at high loads. Below a critical value of the load known as the stress...fracture for the three types of materials differ greatly. Polymers and metals have plastic zones at their crack tips, so that stress corrosion

Evaluation of Additive Manufacturing for Stainless Steel Components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peter, William H.; Lou, Xiaoyuan; List, III, Frederick Alyious

This collaboration between Oak Ridge National Laboratory and General Electric Company aimed to evaluate the mechanical properties, microstructure, and porosity of the additively manufactured 316L stainless steel by ORNL’s Renishaw AM250 machine for nuclear application. The program also evaluated the stress corrosion cracking and corrosion fatigue crack growth rate of the same material in high temperature water environments. Results show the properties of this material to be similar to the properties of 316L stainless steel fabricated additively with equipment from other manufacturers with slightly higher porosity. The stress corrosion crack growth rate is similar to that for wrought 316L stainlessmore » steel for an oxygenated high temperature water environment and slightly higher for a hydrogenated high temperature water environment. Optimized heat treatment of this material is expected to improve performance in high temperature water environments.« less

Demonstrating Nonhexavelent Chrome Steel Conversion Coatings on Stryker High Hard Armor Steel Hatches

DTIC Science & Technology

2014-01-01

29 Draft Joint Test Protocol – Validation of Pretreatments for Steel Armor 68 4.4.7 Rising Step Load (Stress Corrosion Cracking) 4.4.7.1...Cost Assessment 27 9. Schedule of Activities 29 10. Management and Staffing 29 11. References 30 Appendix A. Joint Test Protocol 33 Appendix B...in accordance with the tests delineated in the joint test protocol (JTP) provided in appendix A. The functional performance objectives are

Proceedings of the Triservice Corrosion of Military Equipment Conference (1974) held at Dayton, Ohio on 29-31 Oct 1974. Volume II. Sessions IV through VII

DTIC Science & Technology

1975-09-01

Antonio, Texas Observations on the Stress Corrosion 305 Cracking of High Strength Aluminum Alloys : The Effect of Solution pH E. MacNamara Frankford...mental Fatigue Crack Growth Rates and Corrosion Characteristics of High-Toughness Aluminum Alloy Forgings Sheet and Plate",, Technical Report AFMIrTR-73...T7X51 AND 7075-T7351 ALLOY PLATE Fig. 8 21 I T51i T7X51 T7351 FRAC¶¶JBE SURFACES 0OF DOB SPECINENS SHCWMIU RRATIV SCC GROWTH FOR SEVERAL TEMPERS OF 7075

EPRI-NASA Cooperative Project on Stress Corrosion Cracking of Zircaloys. [nuclear fuel failures

NASA Technical Reports Server (NTRS)

Cubicciotti, D.; Jones, R. L.

1978-01-01

Examinations of the inside surface of irradiated fuel cladding from two reactors show the Zircaloy cladding is exposed to a number of aggressive substances, among them iodine, cadmium, and iron-contaminated cesium. Iodine-induced stress corrosion cracking (SCC) of well characterized samples of Zircaloy sheet and tubing was studied. Results indicate that a threshold stress must be exceeded for iodine SCC to occur. The existence of a threshold stress indicates that crack formation probably is the key step in iodine SCC. Investigation of the crack formation process showed that the cracks responsible for SCC failure nucleated at locations in the metal surface that contained higher than average concentrations of alloying elements and impurities. A four-stage model of iodine SCC is proposed based on the experimental results and the relevance of the observations to pellet cladding interaction failures is discussed.

SNF Interim Storage Canister Corrosion and Surface Environment Investigations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryan, Charles R.; Enos, David G.

2015-09-01

This progress report describes work being done at Sandia National Laboratories (SNL) to assess the localized corrosion performance of container/cask materials used in the interim storage of spent nuclear fuel (SNF). Of particular concern is stress corrosion cracking (SCC), by which a through-wall crack could potentially form in a canister outer wall over time intervals that are shorter than possible dry storage times. In order for SCC to occur, three criteria must be met. A corrosive environment must be present on the canister surface, the metal must susceptible to SCC, and sufficient tensile stress to support SCC must be presentmore » through the entire thickness of the canister wall. SNL is currently evaluating the potential for each of these criteria to be met.« less

Resistance to Fracture, Fatigue and Stress-Corrosion of Al-Cu-Li-Zr Alloys

DTIC Science & Technology

1985-02-19

alloys , in both smooth and notch fatigue conditions, are compared in Figure 15 giving a summary of Mg- effect on S-N fatigue behavior. Several ...crack initiation of conventional aluminum alloys and reported that fatigue cracks were associated with cracked constituent particles in 2024 -T3... fatigue cracks. Kung & Fine (14) investigated surface crack initiation in a 2024 -T4 alloy . They observed that at high stresses most cracks formed

The Expending Retrogression Time of Hot-Extruded Sc-CONTAINING Al-Zn-Mg-Cu Alloy

NASA Astrophysics Data System (ADS)

Shim, Sung-Yong; Kim, Dae-Hwan; Sung, Young-Rock; Ahn, In-Shup; Lim, Su-Gun

In this paper, the retrogression and reaging (RRA) behavior and corrosion properties of Sc-containing Al-Zn-Mg-Cu alloy were observed. The dependence of the mechanical properties and corrosion resistance on the heat treatment condition was measured by hardness, tensile, C-ring and conductivity testing. The retrogression time for recovery of the yield strength of the alloy subjected to T6 treatment was 20 min at 200°C of retrogression temperature, which was longer than that of Al7075 alloy. The results of electrical conductivity and C-ring tests showed that the stress corrosion cracking (SCC) resistance in Sc-containing alloy treated for 20 min at 200°C was improved. These study results demonstrated the ability of the Sc-containing alloy to extend the retrogression time and thereby improve the SCC resistance and mechanical properties.

Effect of exposure cycle on hot salt stress corrosion of a titanium alloy

NASA Technical Reports Server (NTRS)

Gray, H. R.; Johnston, J. R.

1974-01-01

The influence of exposure cycle on the hot-salt stress-corrosion cracking resistance of the Ti-8Al-1Mo-1V alloy was determined. Both temperature and stress were cycled simultaneously to simulate turbine-powered aircraft service cycles. Temperature and stress were also cycled independently to determine their individual effects. Substantial increases in crack threshold stresses were observed for cycles in which both temperature and stress or temperature alone were applied for 1 hour and removed for 3 hours. The crack threshold stresses for these cyclic exposures were twice those determined for continuous exposure for the same total time of 96 hours.

76 FR 19719 - Airworthiness Directives; Saab AB, Saab Aerosystems Model SAAB 2000 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-08

... fretting corrosion; a detailed inspection of the actuator mounting bracket and shock struts for damage, cracks, and signs of corrosion; and doing corrective actions if necessary. Corrective actions include removing corrosion, replacing affected bolts with new bolts, tightening loose nuts, repairing, and...

Stress corrosion cracking of titanium alloys

NASA Technical Reports Server (NTRS)

May, R. C.; Beck, F. H.; Fontana, M. G.

1971-01-01

Experiments were conducted to study (1) the basic electrochemical behavior of titanium in acid chloride solutions and (2) the response of the metal to dynamic straining in the same evironment. The aim of this group of experiments was to simulate, as nearly as possible, the actual conditions which exist at the tip of a crack. One of the foremost theories proposed to explain the propagation of stress corrosion cracks is a hydrogen embrittlement theory involving the precipitation of embrittling titanium hydrides inside the metal near the crack tip. An initial survey of the basic electrochemical literature indicated that surface hydrides play a critical role in the electrochemistry of titanium in acid solutions. A comprehensive analysis of the effect of surface films, particularly hydrides, on the electrochemical behavior of titanium in these solution is presented.

Sensitization of Laser-beam Welded Martensitic Stainless Steels

NASA Astrophysics Data System (ADS)

Dahmen, Martin; Rajendran, Kousika Dhasanur; Lindner, Stefan

Ferritic and martensitic stainless steels are an attractive alternative in vehicle production due to their inherent corrosion resistance. By the opportunity of press hardening, their strength can be increased to up to 2000 MPa, making them competitors for unalloyed ultra-high strength steels. Welding, nevertheless, requires special care, especially when it comes to joining of high strength heat treated materials. With an adopted in-line heat treatment of the welds in as-rolled as well as press hardened condition, materials with sufficient fatigue strength and acceptable structural behavior can be produced. Because of microstructural transformations in the base material such as grain coarsening and forced carbide precipitation, the corrosion resistance of the weld zone may be locally impaired. Typically the material in the heat-affected zone becomes sensitive to intergranular cracking in the form of knife-edge corrosion besides the fusion line. The current study comprises of two text scenarios. By an alternating climate test, general response in a corroding environment is screened. In order to understand the corrosion mechanisms and to localize the sensitive zones, sensitisation tests were undertaken. Furthermore, the applicability of a standard test according to ASTM 763-83 was examined. It was found that the alternative climate test does not reveal any corrosion effects. Testing by the oxalic acid test revealed clearly the effect of welding, weld heat treatment and state of thermal processing. Also application of the standard which originally suited for testing ferritic stainless steels could have been justified.

Cracking characteristics of alloy 690 in thiosulfate containing chloride solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H.H.; Tsai, W.T.

1999-07-01

The cracking characteristics of Alloy 690 in deaerated 1wt% NaCl solution with different Na{sub 2}S{sub 2}O{sub 2} concentrations, namely 0.01, 0.1, 0.2 and 0.5 M, at controlled anodic potentials was investigated by using slow strain rate testing (SSRT) with a strain rate of 1 x 10{sup {minus}6} s{sup {minus}1}. The results showed that the ultimate tensile strength and the ductility increased with increasing the concentration of Na{sub 2}S{sub 2}O{sub 3} at the same anodic potential, but decreased with increasing potential at a fixed concentration of Na{sub 2}S{sub 2}O{sub 3}. Pitting corrosion could occur on Alloy 690 in 1wt% NaCl solutionmore » with the concentration of Na{sub 2}S{sub 2}O{sub 3} {le} 0.1 M, depending on the potential. The susceptibilities of Alloy 690 to pitting corrosion and environmentally-assisted cracking in 1wt% NaCl solution were inhibited with the concentration of Na{sub 2}S{sub 2}O{sub 3} {ge} 0.2M, regardless of the potential.« less

Environmental-Induced Damage in Tin (Sn) and Aluminum (Al) Alloys

NASA Astrophysics Data System (ADS)

Vallabhaneni, Venkata Sathya Sai Renuka

Sn and Al alloys are widely used in various industries. Environmental-induced damage resulting in whiskering in Sn and corrosion in Al account for numerous failures globally every year. Therefore, for designing materials that can better withstand these failures, a comprehensive study on the characterization of the damage is necessary. This research implements advanced characterization techniques to study the above-mentioned environmental-induced damage in Sn and Al alloys. Tin based films are known to be susceptible to whisker growth resulting in numerous failures. While the mechanisms and factors affecting whisker growth have been studied extensively, not much has been reported on the mechanical properties of tin whiskers themselves. This study focuses on the tensile behavior of tin whiskers. Tensile tests of whiskers were conducted in situ a dual beam focused ion beam (FIB) with a scanning electron microscope (SEM) using a micro electro-mechanical system (MEMS) tensile testing stage. The deformation mechanisms of whiskers were analyzed using transmission electron microscopy (TEM). Due to the heterogenous nature of the microstructure of Al 7075, it is susceptible to corrosion forming corrosion products and pits. These can be sites for cracks nucleation and propagation resulting in stress corrosion cracking (SCC). Therefore, complete understanding of the corrosion damaged region and its effect on the strength of the alloy is necessary. Several studies have been performed to visualize pits and understand their effect on the mechanical performance of Al alloys using two-dimensional (2D) approaches which are often inadequate. To get a thorough understanding of the pits, it is necessary for three-dimensional (3D) studies. In this study, Al 7075 alloys were corroded in 3.5 wt.% NaCl solution and X-ray tomography was used to obtain the 3D microstructure of pits enabling the quantification of their dimensions accurately. Furthermore, microstructure and mechanical property correlations helped in a better understanding of the effect of corrosion. Apart from the pits, a surface corrosion layer also forms on Al. A subsurface damage layer has also been identified that forms due to the aggressive nature of NaCl. Energy dispersive X-ray spectroscopy (EDX) and nanoindentation helped in identifying this region and understanding the variation in properties.

Linking Grain Boundary Microstructure to Stress Corrosion Cracking of Cold Rolled Alloy 690 in PWR Primary Water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, Stephen M.; Olszta, Matthew J.; Toloczko, Mychailo B.

2012-10-01

Grain boundary microstructures and microchemistries are examined in cold-rolled alloy 690 tubing and plate materials and comparisons are made to intergranular stress corrosion cracking (IGSCC) behavior in PWR primary water. Chromium carbide precipitation is found to be a key aspect for materials in both the mill annealed and thermally treated conditions. Cold rolling to high levels of reduction was discovered to produce small IG voids and cracked carbides in alloys with a high density of grain boundary carbides. The degree of permanent grain boundary damage from cold rolling was found to depend directly on the initial IG carbide distribution. Formore » the same degree of cold rolling, alloys with few IG precipitates exhibited much less permanent damage. Although this difference in grain boundary damage appears to correlate with measured SCC growth rates, crack tip examinations reveal that cracked carbides appeared to blunt propagation of IGSCC cracks in many cases. Preliminary results suggest that the localized grain boundary strains and stresses produced during cold rolling promote IGSCC susceptibility and not the cracked carbides and voids.« less

Effect of layerwise structural inhomogeneity on stress- corrosion cracking of steel tubes

NASA Astrophysics Data System (ADS)

Perlovich, Yu A.; Krymskaya, O. A.; Isaenkova, M. G.; Morozov, N. S.; Fesenko, V. A.; Ryakhovskikh, I. V.; Esiev, T. S.

2016-04-01

Based on X-ray texture and structure analysis data of the material of main gas pipelines it was shown that the layerwise inhomogeneity of tubes is formed during their manufacturing. The degree of this inhomogeneity affects on the tendency of tubes to stress- corrosion cracking under exploitation. Samples of tubes were cut out from gas pipelines located under various operating conditions. Herewith the study was conducted both for sections with detected stress-corrosion defects and without them. Distributions along tube wall thickness for lattice parameters and half-width of X-ray lines were constructed. Crystallographic texture analysis of external and internal tube layers was also carried out. Obtained data testifies about considerable layerwise inhomogeneity of all samples. Despite the different nature of the texture inhomogeneity of gas pipeline tubes, the more inhomogeneous distribution of texture or structure features causes the increasing of resistance to stress- corrosion. The observed effect can be explained by saturation with interstitial impurities of the surface layer of the hot-rolled sheet and obtained therefrom tube. This results in rising of lattice parameters in the external layer of tube as compared to those in underlying metal. Thus, internal layers have a compressive effect on external layers in the rolling plane that prevents cracks opening at the tube surface. Moreover, the high mutual misorientation of grains within external and internal layers of tube results in the necessity to change the moving crack plane, so that the crack growth can be inhibited when reaching the layer with a modified texture.

Characterization of beta phase growth and experimental validation of long term thermal exposure sensitization of AA5XXX alloys

NASA Astrophysics Data System (ADS)

Zhu, Yakun

The United States Navy has a need for fast, light-weight ships to provide rapid deployment in its operations. Strong and corrosion-resistant aluminum alloys, such as AA5083 (UNS A95083) as well as other AA5XXX alloys, have properties that are well-suited for such applications. However, AA5XXX alloys are susceptible to intergranular corrosion (IGC) and stress corrosion cracking (SCC) because of sensitization which is a consequence of the formation of the grain boundary beta-phase, Al3Mg2, and the anodic dissolution of the beta-phase. Significant research has been performed to measure and understand the effects of time, temperature, stress, and sea water on sensitization and associated intergranular corrosion and stress corrosion cracking under steady-state conditions. In the present work, the behaviors of beta-phase nucleation and growth were characterized using optical and electron microscopy, the relationship between preexisting particles and beta-phase, as well as the effect of different heat treatment times and temperatures on IGC and SCC susceptibility of 5XXX alloys were investigated. Grain boundary beta-phase thickness was measured with high resolution transmission electron microscopy (TEM). The corrosion sensitization susceptibility was evaluated according to the American Society for Testing and Materials (ASTM) standard G67 tests, that is, nitric acid mass-loss testing (NAMLT). Diffusion of Mg is manifested by the thickening of beta-phase along the grainboundary because the grain boundary is considered as the preferential site for beta-phase nucleation. The beta-phase growth rate was monitored using high resolution TEM. The variety of precipitates and their subsequent effects on beta-phase nucleation and growth kinetics was investigated. The existence of various intermetallic particles was observed in both baseline and thermally exposed (70°C and 175°C) samples. These particles are usually either rod-shaped or equiaxed, and rich in Mn, Fe, and Cr. Indexing of lattice planes observed in a few of these particles suggested the composition is Al6Mn or Al6(Mn, Fe, Cr). This research also shows that the beta-phase precipitation occurs between the preexisting Mn rich particles. The basic model for the determination of diffusivity values, the prediction of beta-phase thickness growth, and corrosion sensitization prediction have been improved by new data from this research.

Microstructure and corrosion study of porous Mg-Zn-Ca alloy in simulated body fluid

NASA Astrophysics Data System (ADS)

Annur, Dhyah; Erryani, Aprilia; Lestari, Franciska P.; Nyoman Putrayasa, I.; Gede, P. A.; Kartika, Ika

2017-03-01

Magnesium alloys had been considered as promising biomedical devices due to their biocompatibility and biodegradability. In this present work, microstructure and corrosion properties of Mg-Zn-Ca-CaCO3 porous magnesium alloy were examined. Porous metals were fabricated through powder metallurgy process with CaCO3 addition as a foaming agent. CaCO3 content was varied (1, 5, and 10%wt) followed by sintering process in 650 °C in Argon atmosphere for 10 and 15 h. The microstructure of the resulted alloys was analyzed by scanning electron microscopy (SEM) equipped with energy dispersive spectrometry data (EDS). Further, to examine corrosion properties, electrochemical test were conducted using G750 Gamry Instrument in accordance with ASTM standard G5-94 in simulated body fluid (Hank’s solution). As it was predicted, increasing content of foaming agent was in line with the increasing of pore formation. The electrochemical testing indicated corrosion rate would increase along with the increasing of foaming agent. The porous Mg-Zn-Ca alloy which has more porosity and connecting area will corrode much faster because it can transport the solution containing chloride ion which accelerated the chemical reaction. Highest corrosion resistance was given by Mg-Zn-Ca-1CaCO3-10 h sintering with potential corrosion of  -1.59 VSCE and corrosion rate of 1.01 mmpy. From the microstructure after electrochemical testing, it was revealed that volcano shaped structure and crack would occur after exposure to Hank’s solution

Effect of Stress Corrosion and Cyclic Fatigue on Fluorapatite Glass-Ceramic

NASA Astrophysics Data System (ADS)

Joshi, Gaurav V.

2011-12-01

Objective: The objective of this study was to test the following hypotheses: 1. Both cyclic degradation and stress corrosion mechanisms result in subcritical crack growth in a fluorapatite glass-ceramic. 2. There is an interactive effect of stress corrosion and cyclic fatigue to cause subcritical crack growth (SCG) for this material. 3. The material that exhibits rising toughness curve (R-curve) behavior also exhibits a cyclic degradation mechanism. Materials and Methods: The material tested was a fluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). Rectangular beam specimens with dimensions of 25 mm x 4 mm x 1.2 mm were fabricated using the press-on technique. Two groups of specimens (N=30) with polished (15 mum) or air abraded surface were tested under rapid monotonic loading. Additional polished specimens were subjected to cyclic loading at two frequencies, 2 Hz (N=44) and 10 Hz (N=36), and at different stress amplitudes. All tests were performed using a fully articulating four-point flexure fixture in deionized water at 37°C. The SCG parameters were determined by using a statistical approach by Munz and Fett (1999). The fatigue lifetime data were fit to a general log-linear model in ALTA PRO software (Reliasoft). Fractographic techniques were used to determine the critical flaw sizes to estimate fracture toughness. To determine the presence of R-curve behavior, non-linear regression was used. Results: Increasing the frequency of cycling did not cause a significant decrease in lifetime. The parameters of the general log-linear model showed that only stress corrosion has a significant effect on lifetime. The parameters are presented in the following table.* SCG parameters (n=19--21) were similar for both frequencies. The regression model showed that the fracture toughness was significantly dependent (p<0.05) on critical flaw size. Conclusions: 1. Cyclic fatigue does not have a significant effect on the SCG in the fluorapatite glass-ceramic IPS e.max ZirPress. 2. There was no interactive effect between cyclic degradation and stress corrosion for this material. 3. The material exhibited a low level of R-curve behavior. It did not exhibit cyclic degradation. *Please refer to dissertation for table.

An electrochemical model for hot-salt stress-corrosion of titanium alloys

NASA Technical Reports Server (NTRS)

Garfinkle, M.

1972-01-01

An electrochemical model of hot-salt stress-corrosion cracking of titanium alloys is proposed based on an oxygen-concentration cell. Hydrogen embrittlement is proposed as the direct cause of cracking, the hydrogen being generated as the results of the hydrolysis of complex halides formed at the shielded anode of the electrochemical cell. The model found to be consistent with the diverse observations made both in this study and by many investigators in this field.

Laser Peening for Mitigation of Stress Corrosion Cracking at Welds in Marine Aluminum

DTIC Science & Technology

2011-06-01

therefore leaving the welded area and the HAZ in tension and the surround base metal in compression [ 6 ]. Figure 4 shows the residual stress of a MIG...either by electropolishing or vibratory polishing. The samples were electropolished in a Buehler Electromet 4 Electropolisher using a solution of...REPORT TYPE AND DATES COVERED Master’s Thesis 4 . TITLE AND SUBTITLE Laser Peening for Mitigation of Stress Corrosion Cracking at Welds in Marine

77 FR 55681 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-11

... prompted by reports of stress corrosion cracking in the chord segments made from 7079 aluminum in the... repairing discrepancies if necessary. We are issuing this AD to detect and correct stress corrosion and/or... America Code 55: Stabilizers. (e) Unsafe Condition This AD was prompted by reports of stress corrosion...

78 FR 7647 - Airworthiness Directives; Bombardier, Inc. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-04

... gouges, scratches, and corrosion, and replacing the trunnions if necessary; and adding serial numbers and... section. We are issuing this AD to detect and correct cracking, gouges, scratches, and corrosion of the... trunnions and upper and lower pins for gouges, scratches, and corrosion, and replacing if necessary; and...

76 FR 41665 - Airworthiness Directives; Saab AB, Saab Aerosystems Model SAAB 2000 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-15

... a detailed inspection of the bolts for uniform or fretting corrosion; a detailed inspection of the actuator mounting bracket and shock struts for damage, cracks, and signs of corrosion; and doing corrective actions if necessary. Corrective actions include removing corrosion, replacing affected bolts with new...

Time exposure studies on stress corrosion cracking of aluminum 2014-T6, 2219-T87, 2014-T651, 7075-T651, and titanium 6Al-4V

NASA Technical Reports Server (NTRS)

Terrell, J.

1973-01-01

The effect of a constant applied stress in crack initiation of aluminum 2014-T6, 2219-T87, 2014-T651, 7075-T651 and titanium 6Al-4V has been investigated. Aluminum c-ring specimens (1-inch diameter) and u-band titanium samples were exposed continuously to a 3.5% NaCl solution (pH 7) and organic fluids of ethyl, methyl, and iso-propyl alcohol (reagent purity), and demineralized distilled water. Corrosive action was observed to begin during the first and second day of constant exposure as evidenced by accumulation of hydrogen bubbles on the surface of stressed aluminum samples. However, titanium stressed specimens showed no reactions to its environment. Results of this investigation seems to suggest that aluminum 2014-T6, aluminum 7075-T651 and aluminum 2014-T651 are susceptible to stress corrosion cracking in chloride solution (NaCl), while aluminum 2219-T87 seem to resist stress corrosion cracking in sodium chloride at three levels of stress (25%, 50%, and 75% Y.S.). In organic fluids of methyl, ethyl, and iso-propyl alcohol, 2014-T6 and 7075-T651 did not fail by SCC; but 2014-T651 was susceptible to SCC in methly alcohol, but resistant in ethyl alcohol, iso-propyl alcohol and demineralized distilled water.

Influences of Processing and Fatigue Cycling on Residual Stresses in a NiCrY-Coated Powder Metallurgy Disk Superalloy

NASA Astrophysics Data System (ADS)

Gabb, T. P.; Rogers, R. B.; Nesbitt, J. A.; Miller, R. A.; Puleo, B. J.; Johnson, D.; Telesman, J.; Draper, S. L.; Locci, I. E.

2017-11-01

Oxidation and corrosion can attack superalloy disk surfaces exposed to increasing operating temperatures in some turbine engine environments. Any potential protective coatings must also be resistant to harmful fatigue cracking during service. The objective of this study was to investigate how residual stresses evolve in one such coating. Fatigue specimens of a powder metallurgy-processed disk superalloy were coated with a NiCrY coating, shot peened, and then subjected to fatigue in air at room and high temperatures. The effects of this processing and fatigue cycling on axial residual stresses and other aspects of the coating were assessed. While shot peening did induce beneficial compressive residual stresses in the coating and substrate, these stresses relaxed in the coating with subsequent heating. Several cast alloys having compositions near the coating were subjected to thermal expansion and tensile stress relaxation tests to help explain this response of residual stresses in the coating. For the coated fatigue specimens, this response contributed to earlier cracking of the coating than for the uncoated surface during long intervals of cycling at 760 °C. Yet, substantial compressive residual stresses still remained in the substrate adjacent to the coating, which were sufficient to suppress fatigue cracking there. The coating continued to protect the substrate from hot corrosion pitting, even after fatigue cracks initiated in the coating.

Effect of temperature and dissolved oxygen on stress corrosion cracking behavior of P92 ferritic-martensitic steel in supercritical water environment

NASA Astrophysics Data System (ADS)

Zhang, Z.; Hu, Z. F.; Zhang, L. F.; Chen, K.; Singh, P. M.

2018-01-01

The effect of temperature and dissolved oxygen (DO) on stress corrosion cracking (SCC) of P92 martensitic steel in supercritical water (SCW) was investigated using slow strain rate test (SSRT) and fractography analysis. The SSRT was carried out at temperatures of 400, 500, 600 °C in deaerated supercritical water and at DO contents of 0, 200, 500 ppb at the temperature of 600 °C, respectively. The results of SSRT show that the decrease of ductility at the temperature of 400 °C may be related to the dynamic strain aging (DSA) of P92 steel. The degradation of the mechanical properties in SCW is the joint effect of temperature and SCC. Compared with the effect of temperature, DO in SCW has no significant effect on the SCC susceptibility of P92 steel. The observation of oxide layer shows that large numbers of pores are nucleated in the oxide layer, which is related to vacancy accumulation and hydrogen generated in the oxide layer. Under the combined action of the growth stress and tensile stress, micro cracks, nucleated from the pores in the oxide layer, are easily propagated intergranularly outward to the surface of specimen, and fewer cracks can extend inward along the intrinsic pores to the inner oxide/metal interface, which is the reason for the exfoliation of oxide films.

Critical Issues in Hydrogen Assisted Cracking of Structural Alloys

DTIC Science & Technology

2006-01-01

does not precipitate ? Does the HEAC mechanism explain environment-assisted (stress corrosion ) crack growth in high strength alloys stressed in moist...superalloys were cracked in high pressure (100-200 M~a) H2, while maraging and tempered-martensitic steels were cracked in low pressure (-100 kPa) H2...of IRAC in ultra-high strength AerMet®l00 steel demonstrates the role of crack tip stress in promoting H accumulation and embrittlement. The cracking

Metallurgical investigation into ductility dip cracking in nickel based alloys

NASA Astrophysics Data System (ADS)

Noecker, Fredrick F., II

A690 is a Ni-Cr-Fe alloy with excellent resistance to general corrosion, localized corrosion and stress corrosion cracking. However, the companion filler metal for A690, EN52, has been shown by several researchers to be susceptible to ductility dip cracking (DDC), which limits its widespread use in joining applications. The Gleeble hot ductility test was used to evaluate the DDC susceptibility of A600 and A690, along with their filler metals, EN82H and EN52, throughout the heating and cooling portions of a simulated weld reheat thermal cycle. Both macroscopic mechanical measures and microscopic measures of DDC were quantified and compared. Water quenching was conducted at select temperatures for subsequent microstructural characterization. Microstructural and microchemical characterization was carried out using scanning electron microscopy, transmission electron microscopy and analytical electron microscopy (AEM) techniques. The greatest resistance to DDC was observed in A600 and A690 during heating, where no DDC cracks formed even when the samples were fractured. Both A690 and EN52 were found to form an intermediate on-cooling dip in ductility and UTS, which corresponded to an increase in ductility dip crack length. The hot ductility and cracking resistance of EN82H remained high throughout the entire thermal cycle. DDC susceptibility in both EN52 and EN82H decreased when the thermal cycle was modified to promote coarsening/precipitation of intergranular carbides prior to straining. AEM analysis did not reveal any sulfur or phosphorous intergranular segregation in EN52 at 1600°F on-heating, on-cooling or after a 60 second hold. The ductility dip cracks were preferentially oriented at a 45° to the tensile axis and were of a wedge type appearance, both of which are characteristic of grain boundary sliding (GBS). Samples with microstructures that consisted of coarsened carbides and/or serrated grain boundaries, which are expected to decrease GBS, were found to be resistant to DDC. Based on the results of this work grain boundary sliding contributes to DDC, while sulfur and phosphorous embrittlement do not play a role in DDC of EN52 at the concentrations investigated. The dynamic precipitation of partially coherent intergranular M23C6 carbides at intermediate temperatures may exacerbate DDC in A690 and EN52, but requires further investigation.

Mechanical properties of the rust layer induced by impressed current method in reinforced mortar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Care, S.; Nguyen, Q.T.; L'Hostis, V.

This paper describes the mechanical effects of rust layer formed in reinforced mortar through accelerated tests of corrosion. The morphological and physico-chemical properties (composition, structures) of the corrosion system were characterized at different stages by using optical microscope and scanning electron microscope coupled with energy dispersive spectroscopy. The corrosion pattern was mainly characterized by a rust layer confined at the interface between the steel and the mortar. Expansion coefficient of rust products was determined from the rust thickness and the Faraday's law. Furthermore, in order to understand the mechanical effects of corrosion on the damage of mortar, displacement field measurementsmore » were obtained by using digital image correlation. An analytical model (hollow cylinder subjected to inner and outer pressures) was used with a set of experimental data to deduce the time of cracking and the order of magnitude of the mechanical properties of the rust layer.« less

Boric Acid Corrosion of Concrete Rebar

NASA Astrophysics Data System (ADS)

Pabalan, R. T.; Yang, L.; Chiang, K.–T.

2013-07-01

Borated water leakage through spent fuel pools (SFPs) at pressurized water reactors is a concern because it could cause corrosion of reinforcement steel in the concrete structure and compromise the integrity of the structure. Because corrosion rate of carbon steel in concrete in the presence of boric acid is lacking in published literature and available data are equivocal on the effect of boric acid on rebar corrosion, corrosion rate measurements were conducted in this study using several test methods. Rebar corrosion rates were measured in (i) borated water flowing in a simulated concrete crack, (ii) borated water flowing over a concrete surface, (iii) borated water that has reacted with concrete, and (iv) 2,400 ppm boric acid solutions with pH adjusted to a range of 6.0 to 7.7. The corrosion rates were measured using coupled multielectrode array sensor (CMAS) and linear polarization resistance (LPR) probes, both made using carbon steel. The results indicate that rebar corrosion rates are low (~1 μm/yr or less)when the solution pH is ~7.1 or higher. Below pH ~7.1, the corrosion rate increases with decreasing pH and can reach ~100 μm/yr in solutions with pH less than ~6.7. The threshold pH for carbon steel corrosion in borated solution is between 6.8 and 7.3.

Hot corrosion behavior of magnesia-stabilized ceramic material in a lithium molten salt

NASA Astrophysics Data System (ADS)

Cho, Soo-Haeng; Kim, Sung-Wook; Kim, Dae-Young; Lee, Jong-Hyeon; Hur, Jin-Mok

2017-07-01

The isothermal and cyclic corrosion behaviors of magnesia-stabilized zirconia in a LiCl-Li2O molten salt were investigated at 650 °C in an argon atmosphere. The weights of as-received and corroded specimens were measured and the microstructures, morphologies, and chemical compositions were analyzed by scanning electron microscopy, X-ray energy dispersive spectroscopy, and X-ray diffraction. For processes where Li is formed at the cathode during electrolysis, the corrosion rate was about five times higher than those of isothermal and thermal cycling processes. During isothermal tests, the corrosion product Li2ZrO3 was formed after 216 h. During thermal cycling, Li2ZrO3 was not detected until after the completion of 14 cycles. There was no evidence of cracks, pores, or spallation on the corroded surfaces, except when Li was formed. We demonstrate that magnesia-stabilized zirconia is beneficial for increasing the hot corrosion resistance of structural materials subjected to high temperature molten salts containing Li2O.