Papers by Keyword: Stress Corrosion Cracking (SCC)

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Authors: Tomoyuki Fujishiro, Takahisa Shobu, Koji Kiriyama, Atsushi Yamamoto
Abstract: In-situ diffraction measurements were carried out on a tensile specimen of SUS304 stainless steel using a small autoclave at BL22XU at SPring-8. The temperature of circulating water in the autoclave was changed from room temperature to 561 K under ambient pressure and also under a pressure of 8.8 MPa. Tensile stress of 260 MPa was applied to the specimen at 561 K under 8.8 MPa, and a two dimensional strain distribution was obtained by calculation based on measured lattice spacings of the γ-Fe311 plane under various conditions. The interior region of the specimen showed higher strain compared with that on the surface region. After the tensile deformation in the autoclave, CT images of cross sections of the specimen were taken. Void-like images with about 50 μm in size were observed.
Authors: De Hui Wu, Zhong Yuan Zhang, Zhen Liang Liu, Xiao Hao Xia
Abstract: Three-dimensional (3-D)finite element simulation models are conducted to simulate the in-serviceinspection of the axial stress corrosion cracking (SCC) in ferromagneticpipeline using remote field eddy current (RFEC) probes. In this paper, atypical remote field eddy current probe which is internal to and coaxial withthe pipe is firstly introduced. Then a 3-D finite element simulation model isestablished in ANSYS to analyze the detection of RFEC technology. Finally theRFEC signals are observed when changing the geometric parameters, and thedefinite influences of crack size on the amplitude and phase lag of REFCsignals are evaluated. The results of the investigations are beneficial to thedetection and sizing of SCC in pipelines
Authors: Dong Jin Kim, Hyuk Chul Kwon, Seong Sik Hwang, Hong Pyo Kim
Abstract: Alloy 600(74wt% Ni, 15wt% Cr, 9wt% Fe) is used as a material for steam generator tubing in pressurized water reactors(PWR) due to its high corrosion resistance under a PWR environment whose primary side and secondary side are operated under 340oC, 150bar and 290oC, 50bar, respectively. However, in spite of its outstanding corrosion resistance, a stress corrosion cracking(SCC) which has been one of the most important degradation issues, has occurred occasionally owing to the severe high temperature and pressure condition of a PWR. It is expected that a SCC is deeply related to an electrochemical property of a passive film formed under a high temperature and pressure condition. Therefore an understanding of the basic electrochemical behaviors regarding an anodic dissolution and a passivation of the bare surface of metals and alloys provides important information about a SCC mechanism and control. In the present work, the passive oxide films on Alloy 600 were investigated as a function of the dissolved oxygen content and the pH by using a potentiodynamic polarization, electrochemical impedance spectroscopy(EIS) and a depth profiling by Auger electron spectroscopy(AES). For this purpose, 0.5M H3BO3, 0.5M Na2SO4 and 0.1M NaOH aqueous solutions with/without dissolved oxygen at 300oC were used as the test solutions. The resistance of an oxide formed in an aerated solution was smaller than that in a deaerated solution while the oxide film in the aerated solution was thicker than the oxide film in the deaerated solution.
Authors: Seong Jong Kim, Seok Ki Jang
Abstract: Recently, there has been increased interest in using aluminum alloys in ship construction instead of fiber-reinforced plastic (FRP). This is because aluminum alloy ships are faster, have a greater load capacity, and are easier to recycle than FRP ships. In this study, we investigated the mechanical and electrochemical properties of aluminum alloys using the slow strain rate and potentiostatic tests under various potential conditions. The optimum protection potential range with regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between -1.5 and -0.7 V (SSCE). These results can be used as reference data for ship design.
Authors: Xiao Dong Wang, Rui Ling Jia, Hui Xia Zhang, Hua Jian Lui, Xi Wei Zhai, Fu Rong Chen
Abstract: 7A52 Al alloy plates was welded using twin-wire metal inert gas arc welding (TMW) .Stress corrosion cracking (SCC)behavior of the parent material and the welded specimens was investigated by the slow strain rate tensile(SSRT)test method respectively. Electrochemical impedance spectroscopy (EIS) was conducted to understand electrochemical corrosion behavior of 7A52 Al alloy and its TMW weldment. It was found that the welded specimens exhibited higher SCC susceptibility than the parent materials under SSRT testing in seawater. The EIS result showed that the weld zone exhibited higher corrosion resistance than that of the parent material. Hydrogen embrittlement is a crucial factor that leads to the failure of the welded specimens during SSRT test in seawater.
Authors: Huan Ping Kong, Chang Kui Liu, De Lin Liu, Tao Jiang
Abstract: Between aircraft bearings lugs, plates fracture appeared. The failure mode and cause were analyzed by macro and micro observation, EDS analysis, metallographic examination and hardness testing. The results showed that two bearings’ failure were stress corrosion cracking. Bearings’ failure were related with abnormal force state, material cast loose exceeding the allowed limited values played a catalytic role to crack propagation. It is suggested that bearings material surface protection should be strengthened to improve corrosion resistance, bearings design should be optimized to avoid abnormal tensile stress, and material casting process should be improved to reduce cast loose.
Authors: Michael Law, Vladimir Luzin, Valerie Linton, Erwin Gamboa
Abstract: Stress Corrosion Cracking (SCC) may be a serious problem in gas pipelines. This work studies the hardness and residual stress profiles in two nominally identical sections of adjacent pipe with similar environment and coating, one of which was affected by detectable SCC and the other that was not. The results show changes in texture, residual stress, plastic strain, and hardness at the pipe surface which may be responsible for the altered susceptibility to SCC.
Authors: Zheng Fang Wang
Abstract: U shape brass tube bundle on heat exchanger cracked when it was having ammonia leak test. Sample was made from brass tube fragment, polished the surface of the sample, eroded it with solution of 5% iron trichloride (FeCl3) and 10% hydrochloric acid (HCl), then took photos with Nicon-300 metallographic microscope. The fracture is a kind of stress corrosion cracking, the reason of cracking was analyzed. The technology of test was improved, the method should be paid attention to during brass tube exchanger manufacture was given out too.
Authors: Huai Xiang Cao, Chun Mao Wang, Xing Qi Qiu
Abstract: Backside cracks were found universally in the ultra-low carbon austenitic stainless steel (316LMod) inner linings of urea reactors in recent years, and led to urea reactors leakage. Analyses on the sample revealed that, the backside cracks were caused by the interaction of wet hydrogen sulfide (H2S) and chloride ions (Cl-) stress corrosion cracking (SCC), and H2S played a dominant role. The source of H2S and chloride ions was the leak detection steam. Furthermore, measures to avoid backside cracks in 316LMod inner linings of urea reactors were put forward and verified.
Authors: Ling Yan Zhao, He Xue, Fu Qiang Yang, Yuan Kui Gui
Abstract: Microstructure and material mechanical property in the fusion boundary (FB) region of dissimilar weld joints in light water reactors are quite complicated and different from the bulk material, which make it more susceptible to stress corrosion cracking (SCC) and produce high weld residual stress. To investigate SCC behavior in the FB region of an Alloy 182-A533B dissimilar weld joint, considering the mechanical heterogeneity, mechanical parameters ahead of crack tip with different sampling location are analyzed. It suggests that the stress near crack tip would be significantly higher in a high yield stress material while the strain would be much smaller, and the effect of the material properties around FB region on strain is smaller than that on stress. The result of J-integral indicates FB region would be a barrier when crack in Alloy 182 weld propagates towards LAS.
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