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Title: Hydrogen Embrittlement of Pipeline Steels: Causes and Remediation

Fundamental studies of hydrogen embrittlement of materials using both experimental observations and numerical simulations of the hydrogen/deformation interactions have been conducted. Our approach integrates mechanical property testing at the macro-scale, microstructural analyses and TEM observations of the deformation processes at the micro- and nano-scale, first-principles calculations of interfacial cohesion at the atomic scale, and finite element simulation and modeling at the micro- and macro-level. Focused Ion Beam machining in conjunction with Transmission Electron Microscopy were used to identify the salient micro-mechanisms of failure in the presence of hydrogen. Our analysis of low strength ferritic steels led to the discovery that “quasi-cleavage” is a dislocation plasticity controlled failure mode in agreement with the hydrogen enhanced plasticity mechanism. The microstructure underneath the fracture surface of 304 and 316 stainless steels was found to be significantly more complex than would have been predicted by the traditional models of fatigue. The general refinement of the microstructure that occurred near the fracture surface in the presence of hydrogen was such that one may argue that hydrogen stabilizes microstructural configurations to an extent not achievable in its absence. Finite element studies of hydrogen and deformation field similitude for cracks in real-life pipelines and laboratory fracture specimensmore » yielded that the Single Edge Notch Tension specimen can be used to reliably study hydrogen material compatibility for pipeline structures. In addition, simulation of onset of crack propagation in low strength ferritic systems by void growth indicated that hydrogen can reduce the fracture toughness of the material by as much as 30%. Both experimental observations and numerical studies of hydrogen transport on hydrogen accumulations ahead of a crack tip yielded that dislocation transport can markedly enhance hydrogen populations which in turn can trigger fracture initiation.« less
 [1] ;  [2]
  1. University of Illinois at Urbana-Champaign
  2. University of Wisconsin-Madison
Publication Date:
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Technical Report
Research Org:
University of Illinois at Urbana-Champaign
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
08 HYDROGEN; hydrogen, embrittlement, microstructure, characterization, finite element analysis, hydrogen transport, fracture, decohesion