Papers by Author: Chun Bo Huang

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Authors: Guang Fu Li, Guo Liang Zhang, Jian Jiang Zhou, Chun Bo Huang, Wu Yang
Authors: Chun Bo Huang, Guang Fu Li, Zhan Peng Lu, Jian Min Zeng, Wu Yang
Abstract: The effects of cold working and heat treatment on caustic stress corrosion cracking (SCC) of mill annealed (MA) alloy 800M in boiling solution of 50%NaOH+0.3%SiO2+0.3%Na2S2O3 were investigated by means of microstructure examination, tensile test, X-ray stress analysis, SCC testing of C-rings, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and metallography. The microstructure of alloy 800M under tested conditions was austenite. With a train of 25% by cold working, the grains of alloy 800M became longer, yield strength (YS) and ultimate tensile strength (UTS) increased, elongation (δ ) decreased, residual stress and the susceptibility to SCC increased. With increasing temperature of heat treatment of alloy 800M with cold working, the grains became bigger , residual stress, YS and UTS decreased and δ increased, the susceptibility to SCC of alloy 800M decreased. In boiling caustic solution, SCC cracks on the surfaces of C-ring specimens polarized potentiostatically at –20mV/SCE initiated from pitting and propagated along grain boundaries. AES analysis indicated that the surface films on MA alloy 800M were enriched in nickel and depleted in iron and chromium.
Authors: Wu Yang, Guang Fu Li, Hao Guo, Jian Jiang Zhou, Chun Bo Huang, Jiasheng Bai
Abstract: Effects of some environmental factors on stress corrosion cracking (SCC) of pipeline steel X-70 both in near-neutral pH environments, including NS4 solution and several solutions containing main types of soil in the eastern part of China, and in high pH solution were studied by means of electrochemical measurement and slow strain rate testing (SSRT). The anodic polarization curves showed different features in near-neutral pH and high pH solutions in terms of active-passive transition behavior. In near-neutral pH solutions, the cracking mode was transgranular with the feature of quasi-cleavage, the susceptibility to SCC increased with decreasing potential, pH and temperature as well as increasing CO2, indicating a dominant mechanism of hydrogen induced cracking (HIC). In high pH solutions, the cracking behavior was similar to that in near-neutral pH solutions when the specimens were polarized at cathodic potentials, but quite different at anodic potentials. A comparison of the electrochemical behavior with the SCC potential region indicated a dominant SCC mechanism associated with anodic dissolution (AD) of X70 in high pH solution at anodic potentials. A preliminary experimental potential (E)-pH-SCC diagram has been established for X70 in near-neutral pH environments.
Authors: Guang Fu Li, Chun Bo Huang, Hao Guo, Wu Yang
Abstract: Stress corrosion cracking (SCC) behaviors of pipeline steel X70 in various near-neutral pH soil environments with characteristics of eastern China have been studied through electrochemical measurements and slow strain rate tests (SSRT) at various electrode potentials in four solutions containing different typical soils in eastern China as well as in NS-4 solution. The SCC susceptibility in the four soil solutions was generally higher than that in NS-4 solution. There was a general trend that SCC susceptibility increased with decreasing the potential, suggesting that hydrogen induced cracking probably plays a key role in the cracking at least at low potentials and the parameters of cathodic protection in engineering should be carefully optimized to avoid SCC.
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