11291 Role of Microstructural Anisotropy of Prestressing Steel on the Fractographic Appearance of Hydrogen-Assisted Micro-Damage

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Product Number: 51300-11291-SG

ISBN: 2011 11291 CP

Author: Jesus Toribio, Diego Vergara and Miguel Lorenzo

Publication Date: 2011

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Cold drawn prestressing steel wires are materials with a markedly oriented microstructure as a consequence of the manufacturing (cold drawing) process. In addition, it is well known that such materials usually work in harsh (or aggressive) environments and they are highly susceptible to environmentally assisted cracking (EAC) in general, either pure stress corrosion cracking (SCC) by localized anodic dissolution (LAD) or the even more dangerous phenomenon of hydrogen assisted cracking (HAC), hydrogen assisted fracture (HAF) or hydrogen embrittlement (HE). This study analyzes the influence of microstructural anisotropy of prestressing steel wires on a special fractography associated with hydrogen-assisted micro-damage in pearlite, the so called tearing topography surface (TTS). To this end, fracture surfaces of notched specimens of pearlitic steels subjected to constant extension rate tests (CERT) up to fracture are analyzed, in an environment causing HAF. Generated results show that, in materials with microstructural anisotropy, the fracture surface with TTS fractography tends to take the form of lined up humps ascending a sloped plane. Furthermore, this study proves that hydrogen enhances the effect of microstructural anisotropy of material on the fracture surface.

Keywords: Prestressing steels, hydrogen embrittlement, microstructural orientation, strength anisotropy, cold drawing, tearing topography surface.