YU Fanghua YANG Guohua Shanghai Institute of Nuclear Research
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Academia Sinica
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Shanghai
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ChinaHAN Rongdian WENG Huimin University of Science and Technology of China
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Hefei
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ChinaSHEN Jianian Corrosion Science Laboratory
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Institute of Corrosion and Protection of Metals Academia Sinica
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Shenvang
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China
金属学报(英文版)
The effects of small amount(≥0.05%)of active elements Y and Ce in Fe-25Cr-40Ni al- loy have been investigated on the kinetics of early stage of high temperature oxidation as well as composition and microsructure of oxide film by ion backscattering and slow positron beam.The results show that Y and Ce can reduce evidently the high tem- perature oxidation rate of FeCrNi alloy at early stage and can effectively enhance the Cr_2O_3 formation and retard the oxide formation of Fe and Ni in the surface layer thus the microstructure of the oxide film is improved.Y and Ce enter the oxide film and concentrate within several tens nanometres from surface of the outer layer.The mech- anism of oxidation resistance for Ce is different from Y.Ce can decrease the density of vacancy defects in oxide layer,so the cations are restrained from diffusion outward through vacancies.While Y can control the outward diffusion of cations through va- cancies at the early statge of oxidation(shorter than 12 min),aften that restrained the cations from diffusion outward along grain boundaries up to 60 min oxidation.
关键词:
ion backscattering
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Corrosion Science
The early stages of the evolution of atmospheric corrosion of carbon steels exposed in both a laboratory simulated and a natural atmosphere environment in Shenyang have been observed by in situ scanning electron microscopy. In the case of laboratory cyclic wet-dry tests, even though the chloride content level is very low, filiform corrosion is initiated in the early stage. The filiform corrosion grows in random directions, forming a network of ridges. White nodules nucleate and grow on the ridges during continued corrosion and eventually connect with each other to form the initial corrosion scale. Pits were also found on the surface beneath corrosion products. In the case of a natural atmospheric environment, both filiform corrosion and other localized corrosion, such as pitting and inter-granular attack take place in the initial stage. It is obvious that there is variety of localized corrosion in the initial stage of atmospheric corrosion. (C) 2007 Elsevier Ltd. All rights reserved.
关键词:
steel;atmospheric corrosion;initial stage;localized corrosion;in-situ;iron;electrolyte;thickness
Materials Chemistry and Physics
The corrosion behaviour of CortenA weathering steel has been investigated using a laboratory accelerated test that involved cyclic wet/dry conditions in Qinghai salt lake water diluted 30 times The characteristics of the rust layers on tested samples were observed by SEM and EPMA analyzed by IRS and XRD and studied by polarization and EIS measurements The weight loss was almost linear indicating that the rust layer had no retarding effect on the corrosion process The crystalline components of the rust layers consisted primarily of beta-FeOOH magnetite (Fe(3)O(4)) and gamma-FeOOH As the corrosion proceeded the amount of beta-FeOOH decreased while that of magnetite and gamma-FeOOH increased XRD EDAX and EPMA indicated that the complex corrosion products magnesioferrite (MgFe(2)O(4)) and iowaite (Mg(4)Fe(OH)(8)OCl 4H(2)O) probably existed in the rust layer in which case they will have had an important Influence on the protectiveness of the rust layer The results of electrochemical measurements showed that the rust layer exhibited high reduction reactivity which facilitated the corrosion of weathering steel in the wetting process The large rust capacitance and small rust resistance indicated that the rust layer had a loose and porous structure which provided poor protection (c) 2010 Elsevier B V All rights reserved
关键词:
Elements;Corrosion test;Electrochemical techniques;Electron probe;low-alloy steels;atmospheric corrosion;carbon-steel;electrochemical;impedance;room-temperature;rust layers;iron;mechanism;products;environment
Surface & Coatings Technology
Using a halide-activated pack-cementation method but at a temperature (600 degrees C) noticeably lower than normal, an eta-Fe(2)Al(5) coating and two delta-Ni(2)Al(3) coatings with and without dispersions of CeO(2) nanoparticles were developed respectively on a low-carbon steel and the steel pretreated with an electrodeposited film of Ni or Ni-CeO(2). The erosion-corrosion (E-C) performance of the three aluminide coatings during 100 h exposure at similar to 600 degrees C in a coal-firing laboratory-scale fluidized-bed combustor (FBC) was investigated, by mounting the aluminized samples onto a rig which maintained rotation for accelerating the relative impacting speed of flying solid particles (mainly SiO(2) bed materials). The eta-Fe(2)Al(5) and the CeO(2)-free delta-Ni(2)Al(3) coatings experienced an unacceptable recession rate. Compared to the two CeO(2)-free aluminide coatings, the CeO(2)-dispersed delta-Ni(2)Al(3) coating offered profoundly improved E-C resistance, because the latter coating was not only strengthened by the CeO(2) dispersion and grain refinement, it also could grow a more adherent alumina scale. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Erosion-corrosion;CeO(2)-dispersion-strengthening;Aluminizing coating;Grain refinement;Hardening;Reactive element effect;oxidation resistance;reactive elements;alloy-steels;water-vapor;power-plant;nickel;combustion;mechanisms;additions;behavior
QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
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Beijing
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China
金属学报(英文版)
The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.
关键词:
stress corrosion cracking
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LIU Guoquan Department of Materials Science and Engineering
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University of Science and Technology Beijing
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100083
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China.
材料科学技术（英文）
Quantitative analysis of populations having a geometric structure,which has developed into a special scientific subject called microstructology or stereology,is of great importance to the characterization and evaluation of microstructures and their evolution in various processes.This paper, besides a brief discussion on those topics such as the recent developments of computer assisted image analysis,mathematical morphology,and fractal analysis,will mainly focus on the scope,fundamen- tals,present status,and perspectives of classical stereology.Several case examples of its application to materials science will also be given.
关键词:
stereology
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XIAO Kui
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DONG Chaofang
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LI Xiaogang
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WANG Fuming
钢铁研究学报(英文版)
The formation and development of corrosion products on carbon steel surface during the initial stage of atmospheric corrosion in a laboratory simulated environment have been studied by scanning electron microscopy (SEM) and Raman spectroscopy. The results showed that two different shapes of corrosion products, that is, ring and chain, were formed in the initial stage of corrosion. MnS clusters were found in the nuclei of corrosion products at the active local corrosion sites. The ringshaped products were composed of lepidocrocite (γFeOOH) and maghemite (γFe2O3) transformed from lepidocrocite. The chaintype products were goethite (αFeOOH). A formation mechanism of the corrosion products is proposed.
关键词:
atmospheric corrosion;corrosion product;carbon steel
Y.Z. Luo
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D.Y. Yu
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Z.M. Xu
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Y. Luo
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G.T. Qi and J.L. Yang Departent of Chemistry
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Huazhong University of Science and Technology
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Wuhan 430074
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China
金属学报(英文版)
The corrosion behaviors of different material in the condensate water from the natural gas purifying station were studied by laboratory tests, field tests and measurements of polarization curve. The results showed that hot dipping aluminum steel had a good corrosion resistance to the accompanying gas of crude oil and condensate water in the natural gas purifying station.
关键词:
condencate water
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null
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