Role of Crystallographic Texture in Hydrogen-Induced Cracking of Low Carbon Steels for Sour Service Piping
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HYDROGEN-INDUCED cracking (HIC) occurs in low carbon steels used in line pipes and pressure vessels carrying wet sour hydrocarbons. The nascent hydrogen produced at the corroding pipe surface diffuses into the steel and precipitates as molecular hydrogen at nonmetallic inclusions, ferrite-pearlite interfaces, martensite islands, and grain boundaries.[1] At these traps, the pressure developed by molecular hydrogen increases to a level at which cracks initiate and propagate either in a straight way parallel to the rolling plane or in a stepwise manner.[1–4] The resistance to HIC of sour service steels can be improved by adopting several strategies. Among them, the reduction in sulfur content, the control of inclusion morphology, and the use of low segregated, uniform microstructures are the most adopted.[1,5] These strategies have proven not to be totally effective in the prevention of HIC in severe conditions.[1,4,6] Therefore, the control of other metallurgical aspects that could improve HIC resistance is desirable. In this sense, the control of crystallo-
graphic texture (or simply texture or macrotexture* ) *The terms macrotexture, microtexture, and mesotexture refer to the average sample texture, the crystallographic orientation of a microstructure point, and the texture of grain boundaries, respectively.[7]
and grain boundary distribution (or mesotexture)[7] seems to be a logical step toward this goal. The fact that texture can play a significant role on fatigue crack growth has been corroborated through experimental and modeling studies.[8,9] Texture is also expected to play a major role in reducing HIC, because it can determine the availability of low resistance paths for crack propagation. In addition to that, texture can be effectively controlled during the steel forming process.[10] In one of the earliest attempts to consider texture with regard to HIC, Miyoshi et al.[3] showed that carbon-manganese steel specimens with a marked {001}-{113}//ND** texture **The notation {hkl}//ND indicates that the {hkl} planes lie parallel to the rolling plane.[7]
V. VENEGAS, Postdoctoral Fellow, F. CALEYO, Associate Professor, and J.M. HALLEN, Professor, are with the Departamento de Ingenierı´ a Metalu´rgica, IPN-ESIQIE, UPALM Edif. 7, Zacatenco, Me´xico, D.F. 07738, Me´xico. T. BAUDIN, Professor, and R. PENELLE, Professor, are with the Laboratoire de Physico-Chimie de l’Etat Solide, ICMMO, UMR CNRS 8182, Baˆtiment 410, Universite´ de Paris Sud, 91405, Orsay, Cedex, France. Contact e-mail: fcaleyo@gmail. com Manuscript submitted October 9, 2006. Article published online April 21, 2007. 1022—VOLUME 38A, MAY 2007
manifest a larger resistance to HIC than specimens with nearly random texture. Surprisingly, these authors concluded that the influence of texture to HIC was not significant. In contrast, Verdeja et al.[4] have recently postulated that the presence of a {110}{332}//ND texture is expected to reduce the sensitivity to HIC of ferritic-pearlitic steels, while the presence of a {001}-{113}-{112}//ND texture will p
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