Elucidating the variables affecting accelerated fatigue crack growth of steels in hydrogen gas with low oxygen concentrations

B. P. Somerday, P. Sofronis, K. A. Nibur, C. San Marchi, R. Kirchheim

Research output: Contribution to journalArticle

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Abstract

The objective of this study was to quantify the effects of mechanical and environmental variables on oxygen-modified accelerated fatigue crack growth of steels in hydrogen gas. Experimental results show that in hydrogen gas containing up to 1000 v.p.p.m. oxygen fatigue crack growth rates for X52 line pipe steel are initially coincident with those measured in air or inert gas, but these rates abruptly accelerate above a critical ΔK level that depends on the oxygen concentration. In addition to the bulk gas oxygen concentration, the onset of hydrogen-accelerated crack growth is affected by the load cycle frequency and load ratio R. Hydrogen-accelerated fatigue crack growth is actuated when threshold levels of both the inert environment crack growth rate and Kmax are exceeded. The inert environment crack growth rate dictates the creation of new crack tip surface area, which in turn determines the extent of crack tip oxygen coverage and associated hydrogen uptake, while Kmax governs the activation of hydrogen-assisted fracture modes through its relationship to the crack tip stress field. The relationship between the inert environment crack growth rate and crack tip hydrogen uptake is established through the development of an analytical model, which is formulated based on the assumption that oxygen coverage can be quantified from the balance between the rates of new crack tip surface creation and diffusion-limited oxygen transport through the crack channel to this surface. Provided Kmax exceeds the threshold value for stress-driven hydrogen embrittlement activation, this model shows that stimulation of hydrogen-accelerated crack growth depends on the interplay between the inert environment crack growth increment per cycle, load cycle frequency, R ratio and bulk gas oxygen concentration.

Original languageEnglish
Pages (from-to)6153-6170
Number of pages18
JournalActa Materialia
Volume61
Issue number16
DOIs
Publication statusPublished - Sep 1 2013

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Steel
Fatigue crack propagation
Hydrogen
Gases
Oxygen
Crack propagation
Crack tips
Chemical activation
Noble Gases
Hydrogen embrittlement
Steel pipe
Inert gases
Analytical models
Cracks
Air

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Cite this

Elucidating the variables affecting accelerated fatigue crack growth of steels in hydrogen gas with low oxygen concentrations. / Somerday, B. P.; Sofronis, P.; Nibur, K. A.; San Marchi, C.; Kirchheim, R.

In: Acta Materialia, Vol. 61, No. 16, 01.09.2013, p. 6153-6170.

Research output: Contribution to journalArticle

Somerday, B. P. ; Sofronis, P. ; Nibur, K. A. ; San Marchi, C. ; Kirchheim, R. / Elucidating the variables affecting accelerated fatigue crack growth of steels in hydrogen gas with low oxygen concentrations. In: Acta Materialia. 2013 ; Vol. 61, No. 16. pp. 6153-6170.
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