Steel In High Temperature Water Research Articles

Intergranular Stress Corrosion Cracking of Platinum Treated Type 304 Stainless Steels in High Temperature Water

Intergranular Stress Corrosion Cracking of Platinum Treated Type 304 Stainless Steels in High Temperature Water

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (V)

The difference in electrochemical corrosion potential of stainless steel exposed to high temperature pure water containing hydrogen peroxide (H2O2) and oxygen (O2)is caused by differences in chemical form of oxide films. In order to identify differences in oxide film structures on stainless steel after exposure to H2O2 and O2 environments, characteristics of the oxide films have been examined by multilateral surface analyses, e.g., X-ray diffraction (XRD), Rutherford back scattering spectroscopy (RBS), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). Preliminary characterization results of oxide films confirmed that the oxide film formed under the H2O2 environment consists mainly of hematite (α-Fe2O2), while that under the O2 environment consists of magnetite (Fe3O4). Furthermore oxidation at the very surface of the film is much more enhanced under the H2O2 environment than that under the O2 environment. It was speculated that metal hydroxide plays an important role in oxidation of stainless steel in the presence of H2O2. The difference in electric resistance of oxide film causes the difference in anodic polarization properties. It is recommended that several anodic polarization curves for specimens with differently oxidized films should be prepared to calculate ECP based on the Evans diagram.

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (V). Characterization of Oxide Film on Stainless Steel by Multilateral Surface Analyses.

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (V). Characterization of Oxide Film on Stainless Steel by Multilateral Surface Analyses.

Mechanochemical model to predict stress corrosion crack growth of stainless steel in high temperature water

This paper presents a predictive methodology for SCC crack growth using a mechanochemical model based on a slip formation/dissolution mechanism. The mechanochemical model consists of the combined kinetics of the plastic deformation process as a mechanical factor and the slip dissolution–repassivation process as an environmental factor at a crack tip. The predictive equation of SCC crack growth rate for type 304 SS in water at 288°C is formulated as a function of stress intensity factor, material conditions (degree of sensitization, K ISCC, strain hardening coefficient) and water chemistry (water conductivity, corrosion potential). The theoretical predictions according to the mechanochemical model are quantitatively in good agreement with many experimental observations of the effect on SCC crack growth for type 304 SS in 288°C water.

Effects Of Hydrogen Peroxide On Intergranular Stress Corrosion Cracking Of Stainless Steel in High Temperature Water, (IV)

In order to determine the effects of hydrogen peroxide on electrochemical corrosion potential (ECP) of type 304 stainless steel (SUS304), ECPs were measured using a high temperature, high pressure water loop with polytetrafluoroethylene (PTFE) inner liner at controlled hydrogen peroxide concentration. It is observed that the ECP of SUS304 exposed to hydrogen peroxide is higher than that when exposed to oxygen at the same oxidant concentration. The ECP shows a hysteresis pattern for its concentration dependency. Those results were attributed mainly from the chemical form of oxide film on stainless steel specimens. The oxide film was affected by the corrosive circumstances. Hematite (α-Fe2 O3) was observed for the specimens exposed to hydrogen peroxide, while Fe3O4 was a main oxide when exposed to oxygen. The difference of the anodic polarization curves between O2 and H2O2 environments was caused by the difference of the stability between α-Fe2O3 and Fe3O4. Since the α-Fe2O3 is reduced to the Fe2+ when hydrogen is added to water, the ECP decreases with decreasing oxidant concentration without showing the hysteresis that keep the ECP higher value.

Development of Deformation Instability During the Low Cycle Fatigue Testing of F82H Steel in High Temperature Water

Load-controlled low cycle fatigue tests were carried out on the reduced activation martensitic steel, F82H modified, in pure oxygen-free water at 240°C, thus simulating the most viable coolant chemistry for fusion reactors. It was found that water determined cyclic life reduction as compared to the base-line data in air. Depending on the mechanical parameters employed, the fracture modes were either of the fatigue type and associated with subcritical crack nucleation and stable propagation assisted by the aqueous environment, or almost completely plastic due to the onset of deformation instability which preceded any environmentally-induced cracking process.The results presented in this paper will be discussed in terms of individual concurrent damaging mechanisms, either time or cycle dependent. Possible causative factors are also suggested for further assessments concerning the cyclic response variability observed in specimens from different lots having, a priori, the same history.

Effect of Neutron Irradiation on Stress Corrosion Cracking of Sensitized Type 304 Stainless Steel in High-Temperature Water

Abstract An in-core constant load test was carried out to examine the effect of pre-irradiation on the intergranular stress corrosion cracking (IGSCC) behavior of thermally sensitized Type 304 stainless steel ([SS] UNS S30400) in a simulated boiling water reactor (BWR) water environment. It was shown that, in constant load tests, preirradiated, thermally sensitized Type 304 SS had a lower IGSCC susceptibility, a larger time to failure, than unirradiated, thermally sensitized SS for a given stress level. An out-of-core constant load test and interrupt slow strain rate tensile (SSRT) tests also were carried out to discuss the in-core test result on unirradiated, thermally sensitized Type 304 SS, simulating radiation hardening by work hardening. The out-of-core tests, with surface observations, suggested that an increase in proof strength by neutron irradiation would be the main cause of the lower IGSCC susceptibility of the preirradiated Type 304 SS, since the increase in proof strength would prevent a form...

ステンレス鋼の高温水中SSRT試験におけるSCCき裂の直接観察

ステンレス鋼の高温水中SSRT試験におけるSCCき裂の直接観察

Predicting SCC Behaviour of Austenitic Stainless Steels in High Temperature Water by Empirical Learning Methods(EAC2)

Predicting SCC Behaviour of Austenitic Stainless Steels in High Temperature Water by Empirical Learning Methods(EAC2)

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (IV) Effects of Oxide Film on Electrochemical Corrosion Potential.

In order to determine the effects of hydrogen peroxide on electrochemical corrosion potential (ECP) of type 304 stainless steel (SUS304), ECPs were measured using a high temperature, high pressure water loop with polytetrafluoroethylene (PTFE) inner liner at controlled hydrogen peroxide concentration. It is observed that the ECP of SUS304 exposed to hydrogen peroxide is higher than that when exposed to oxygen at the same oxidant concentration. The ECP shows a hysteresis pattern for its concentration dependency. Those results were attributed mainly from the chemical form of oxide film on stainless steel specimens. The oxide film was affected by the corrosive circumstances. Hematite (α-Fe2 O3) was observed for the specimens exposed to hydrogen peroxide, while Fe3O4 was a main oxide when exposed to oxygen. The difference of the anodic polarization curves between O2 and H2O2 environments was caused by the difference of the stability between α-Fe2O3 and Fe3O4. Since the α-Fe2O3 is reduced to the Fe2+ when hydrogen is added to water, the ECP decreases with decreasing oxidant concentration without showing the hysteresis that keep the ECP higher value.

Radiation-induced preferential dissolution of specific planes of carbon steel in high-temperature water

With respect to carbon steel, corrosion examinations are performed in boiling water under the conditions of with and without exposure to γ-rays. Simulating a radiation-induced concentration cell, one set of samples is connected to the anode of external battery, while the other to the cathode. The corrosion current monitored during the corrosion and weight loss measurement after a prescribed corrosion period have revealed that corrosion rate under γ-rays is six times larger as that under a non-irradiated condition. An interesting feature observed by XRD analysis is that γ-ray exposure remarkably enhances the preferential dissolution of a specific (1 1 0) plane, which potentially triggers an occurrence of the pitting corrosion and an incipient crack; tensile stress being superposed, cracks like IASCC are implied to readily initiate and propagate through materials. Several measures against IASCC often found in the existing nuclear plants are envisaged in the light of controlling a radiation-induced concentration cell formation reported before.

Status of JAERI Material Performance Database (JMPD) and Analysis of Irradiation Assisted Stress Corrosion Cracking (IASCC) Data

A material performance database for nuclear applications, which was named the JAERI Material Performance Database (JMPD), has been developed since 1986 with a view to utilizing various kinds of characteristic data of nuclear materials efficiently. The data stored in the JMPD are mainly fatigue crack growth data on low alloy steels, creep data on superalloys, tensile data on aluminum alloys and stress corrosion cracking data (Slow Strain Rate Testing (SSRT), crack growth rate, etc.) on austenitic stainless steels. Irradiation Assisted Stress Corrosion Cracking (IASCC) of austenitic stainless steels in high temperature water has been considered as a degradation phenomenon potential not only in light water reactors (LWRs) but in the rather common systems where the materials are exposed to radiation in the presence of water. This paper describes the present status of the JMPD, which is partially available through the Internet. Furthermore, some trials for the utilization of the system focused on the issues relating to IASCC are mentioned. The effect of alloy composition, dissolved oxygen and neutron fluence on IASCC susceptibilities and SCC growth rate could be drawn.

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (III)

The stress corrosion cracking (SCC) of structural materials used in boiling water reactors has been studied at relatively low hydrogen peroxide (H2O2) concentrations, around lOppb, which was assumed to be representative of the corrosion environment formed in hydrogen water chemistry (HWC). The 1/4T compact tension specimen was used for measurement of crack growth rates (CGRs) of sensitized type 304 stainless steel in high temperature and high purity water. Crack length was monitored by a reversing direct current potential drop method. Since H2O2 is easily decomposed thermally, a polytetrafluoroethylene-lined autoclave was used to minimize its decomposition on the autoclave surface. The CGR in the H2O2 environment differed from that in the O2 environment even though the electrochemical corrosion potential (ECP) for both conditions was the same. The data implied that the ECP could not be used as a common environmental deterministic parameter for SCC behavior at higher potentials for different oxidant conditions. The corrosion current density was found to play an important role as an environmental index for SCC, which was given as just the current density at the ECP at a specific oxidant concentration. The CGRs were found to be written as CGR = (3.8±0.6)xl0-3 icor +(l-5±1.6) x 10-8mm/s using the calculated corrosion current density icorbelow 10-4 A-cm-2.

Irradiation-enhanced corrosion of carbon steel in high temperature water — in view of a cell formation induced by γ-rays

A corrosion study of carbon steel, with and without exposure to γ-rays, has been carried out in water at high temperature and much attention was paid to the effect of radiation-induced cell formation. The measurement of weight changes during corrosion has revealed that the corrosion rate under a dose of 0.48 kGy/h is six times larger than that without exposure. No substances other than Fe 3O 4 and α-iron with an anomalous X-ray diffraction (XRD) pattern are identified on the surface after corrosion. The XRD and scanning electron microscope (SEM) analyses have shown that, an enhancement of the preferential dissolution of α-iron(110) proceeds on the specimens in contact with those unirradiated, whereas this type of dissolution is suppressed on the isolated specimens. On the other hand, an increased deposit of Fe 3O 4 is observed when an isolated condition is employed during corrosion under exposure. Taking the results into consideration, it is suggested that irradiation-assisted stress corrosion cracking (IASCC) could be prevented from occurring by electrically isolating the in-core components from the out-of-core materials.

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (II)

In order to determine a crack propagation rate of less than 10-8 mm/s in a 24-hour integrated measurement, major parameters of a coupled system of a constant tension specimen and crack depth measurement, based on potential drop method, have been optimized. Influences of sensor geometry, location for detecting potential drop and data processing of the ratio of signal to noise (S/N) were optimized by applying Taguchi's Method. Then a suitable sensor geometry and data processing method were proposed to get a robust measurement system with higher sensitivity and lower susceptibility for geometrical and procedural fluctuations. By applying the optimal crack propagation rate measurement system, it was confirmed that a crack propagation rate of lxlO-8 mm/s can be measured under a low concentration condition of hydrogen peroxide with less than a 20% error by a 24-hour integrated measurement.

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (III). Crack Growth Rates in Corrosive Environment Determined by Hydrogen Peroxide.

The stress corrosion cracking (SCC) of structural materials used in boiling water reactors has been studied at relatively low hydrogen peroxide (H2O2) concentrations, around lOppb, which was assumed to be representative of the corrosion environment formed in hydrogen water chemistry (HWC). The 1/4T compact tension specimen was used for measurement of crack growth rates (CGRs) of sensitized type 304 stainless steel in high temperature and high purity water. Crack length was monitored by a reversing direct current potential drop method. Since H2O2 is easily decomposed thermally, a polytetrafluoroethylene-lined autoclave was used to minimize its decomposition on the autoclave surface. The CGR in the H2O2 environment differed from that in the O2 environment even though the electrochemical corrosion potential (ECP) for both conditions was the same. The data implied that the ECP could not be used as a common environmental deterministic parameter for SCC behavior at higher potentials for different oxidant conditions. The corrosion current density was found to play an important role as an environmental index for SCC, which was given as just the current density at the ECP at a specific oxidant concentration. The CGRs were found to be written as CGR = (3.8±0.6)xl0-3 icor +(l-5±1.6) x 10-8mm/s using the calculated corrosion current density icorbelow 10-4 A-cm-2.

Influence of beach mark loading and precrack length on fatigue crack growth rate of A533B steel in high temperature water

Influence of beach mark loading and precrack length on fatigue crack growth rate of A533B steel in high temperature water

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (II) Optimization of Crack Propagation Rate Measurement System.

Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (II) Optimization of Crack Propagation Rate Measurement System.

高温水中におけるニッケル基合金及びステンレス鋼の応力腐食割れ成長モデル

高温水中におけるニッケル基合金及びステンレス鋼の応力腐食割れ成長モデル

Stress Corrosion Crack Rate of STS 304 Stainless Steel in High Temperature Water

Sensitized STS 304 stainless steel crack growth rate(CGR) in high temperature water was investigated under trapezoidal wave loading test using fracture mechanics techniques. The CGR, due to stress corrosion cracking(SCC), were systematically measured as a function of the stress intensity factor and stress. holding time under trapezoidal wave loading. In high temperature water, CGR was enhanced by a synergistic effects in combination with an aggressive environment and mechanical damage. The CGR, was basically described as a summation of the environmentally assisted crack growth rate , and fatigue crack growth rate in air $(da/dN)air,. The CGR, , increased linearly with increasing stress holding time. The CGR, decreased linearly with increasing stress holding time. Fracture surface mode varied from trans-granular cracking to inter-granular cracking with increasing stress holding time.