Papers by Keyword: Intergranular Corrosion (IGC)

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Authors: Timothy J. Harrison, Bruce R. Crawford, Graham Clark, Milan Brandt
Abstract: This paper presents a model that predicts the stress field around intergranular corrosion. The stress analysis is conducted in ABAQUS via a Python input script, which is written in Igor Pro. The intergranular corrosion path is described using a Monte-Carlo Markov Chain based on the materials grain size distribution and probability that the corrosion will turn at a grain boundary junction. The model allows a complete analysis of the stresses resulting from intergranular corrosion around a fastener hole of any size. As fatigue initiation is most likely to occur at the highest stress concentration, this model gives an understanding of which of the features of intergranular corrosion are most critical and can allow for the development of beta solutions for crack growth. This model has been applied to 7075-T651 extruded aluminum alloy from a legacy era aircraft but can be readily applied to any material where the microstructure is known and can be described using a statistical distribution.
Authors: L. Tan, Kumar Sridharan, T.R. Allen
Abstract: Grain boundary engineering (GBE) was employed to improve the oxide exfoliation resistance and mitigate oxide growth by optimizing the grain boundary character distribution. Studies were performed on alloys of Incoloy 800H and Inconel 617. Alloys 800H and 617 were selected due to their potential applications for the Generation IV nuclear power systems. The effect of GBE on the corrosion response was evaluated using supercritical water exposure tests and cyclic oxidation tests. The microstructure of the tested samples was analyzed by means of optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction, and gravimetry. The effects of thermal expansion mismatch and Cr volatilization on the corrosion response are discussed.
Authors: Kui Xiao, Dan Wei, Xin Zhang, Xue Qun Cheng, Jun Sheng Wu, Xiao Gang Li
Abstract: In this work, analysis was performed to investigate the reasons resulting in corrosion of 316L of heat exchanger tube in the producing glycine process. Results demonstrated that corrosion of 316L is attributed to intergranular corrosion of nonsensitized. Intergranular corrosion of nonsensitized occurs of 316L, the elements of Si, Ni, Mo are clustering, and the carbon oxide increases corrosion.
Authors: Huai Bei Zheng, Xiao Ning Ye, Zheng Cai, Lai Zhu Jiang, Zhen Yu Liu, Guo Dong Wang, Bao Sen Wang
Abstract: Intergranular corrosion in heat-affected zone of low carbon 12Cr-Ni ferritic stainless steel was investigated by the method of practice Z in ASTM A 763-93. The microstructure of welded joint was characterized using an optical microscope and a scanning electronic microscope. Severe intergranular corrosion (IGC) was only observed in low temperature heat-affected zone (LTHAZ) adjacent to base metals at the back of the welded joints in unstabilized steel. On the other hand, IGC was not observed in the welded joints of stabilized steels. According to the analysis of microstructure, the severe IGC is attributed to both the precipitated phase along the grain boundaries inducing the presence of chromium-depleted zone and the welding residual tensile stress promoting the corrosion. Therefore, stabilized elements addition such as Ti and Nb is required in order to avoid the IGC in welded joint of these steels. Relief residual tensile stress by post weld heat treatment would also be an effective method to avoid the IGC in the welded joints of these steels.
Authors: James T. Staley, S.C. Byrne, E.L. Colvin, K.P. Kinnear
Authors: Sergio Baragetti, M. Daurù, Riccardo Gerosa, Barbara Rivolta
Abstract: In the present experimental work, a WC/C coated 7075-T6 aluminum alloy was considered from the corrosion point of view. The coating was deposited by PVD technique with a final thickness of about 2.5μm. In order to study the influence of the coating on the corrosion behavior of the aluminum alloy, the samples surfaces were partially coated and the interface among the metal and the coating was analyzed after the corrosion tests described into the ASTM G110 standard. Such experimental plan was decided in order to simulate the possible in-service local removal of the thin and hard coating. This kind of damage, due for example to a foreign object impact, can occur because of the great hardness difference between the coating and the substrate. The experimental tests were carried out on samples with different surface finishing, ranging from about 0.02μm Ra (mirror-polished surface) to about 0.8μm Ra (320 grit paper). The aim of such choice was to investigate the effect of a surface roughness different from the optimal one (mirror polished) on the coating deposition. Moreover a different corrosion resistance is expected.
Authors: Takura Mimaki, Masashi Yamashita, S. Hashimoto, S. Miura
Authors: Vivekanand Kain, Shagufta Khan, A.V.R. Reddy, P.K. Wattal
Abstract: The austenitic stainless steels are used in nuclear spent fuel reprocessing and waste management plants and the process fluid is nitric acid at temperature up to boiling point. However incorporation of oxidizing ions e.g. fission products as well as corrosion products, in nitric acid stream make the environment highly corrosive to stainless steels. Present work aims to investigate role of process parameters and material parameters (composition and microstructure) on corrosion behaviour of stainless steels. The process parameters studied are temperature, acid concentration and oxidizing ions. It has been shown that the potential attained on stainless steel is a function of acid concentration and temperature and is further strongly affected by addition of oxidizing ions. This developed potential determines the corrosion behaviour of stainless steel. Increasing the temperature and concentration of nitric acid and concentration of oxidizing species increased the developed potential. Potentials were applied to types 304 L (nitric acid grade - NAG), 304 L (commercial purity) and 310 L stainless steels in boiling 6 M nitric acid for a period of 48 h. The corrosion rates measured in such experiments were plotted as a function of applied potential. The form of corrosion was established by microstructural examination. A clear demarcation was observed between uniform corrosion and intergranular corrosion at a potential of 960-980 mVSCE. Above this potential range corrosion rate increased exponentially and the form of corrosion is shown to be intergranular corrosion. Below this potential range, uniform and low rate of corrosion occurred. The influence of microstructure (step, dual and ditch) of type 304 L was also studied and is described in this paper.
Authors: H. Uchida, Hideo Yoshida, Hirohito Hira, Takumi Amano
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