Effect of inclusions on initiation of stress corrosion cracks in X70 pipeline steel in an acidic soil environment |
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Authors: | Z.Y. Liu C.W. Du Y.R. Zhang Y.F. Cheng |
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Affiliation: | a Corrosion and Protection Center, University of Science and Technology, Beijing, Beijing 100083, China b Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4 c Mechanical Engineering Department, University of Rochester, NY 14627, USA |
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Abstract: | The effect of inclusions on the initiation of stress corrosion cracking (SCC) X70 pipeline steel was investigated in an acidic soil solution using slow strain rate test, scanning electron microscopy and energy-dispersive X-ray techniques. The results demonstrated that stress corrosion cracks are not initiated in X70 steel when it is under anodic polarization. At cathodic polarization, hydrogen evolution is enhanced, and hydrogen is actively involved in SCC processes. Two types of inclusions exist in the steel and play different role in crack initiation. The inclusions enriching in Al are brittle and incoherent to the metal matrix. Microcracks and interstices are quite easily to be resulted in at the boundary between inclusions and metal. There is no crack initiating at inclusions containing mainly Si. |
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Keywords: | A. Steel B. SEM C. Inclusion C. Stress corrosion |
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