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Chapter 3
Measurement and Modeling of Temperature Dependent Internal Hydrogen Assisted Cracking in Cr-Mo Steel

Excerpt

The intrinsic temperature dependence of internal hydrogen assisted cracking (IHAC) of 2¼Cr-1Mo steel base plate and weld metal is measured with several fracture mechanics approaches, including a new-slotted specimen. Slow-rising displacement threshold stress intensity (KIH) increases as IHAC is eliminated with rising temperature from -50 to 125°C. Hydrogen concentration proximate to the crack tip (C), stress enhanced and microstructure trapped, provides a similitude parameter; equal KIH is produced for equal C. The C from FEA diffusion analysis decreases with decreasing-bulk H concentration and decreasing-exponential of the H-binding energy to temperature ratio for trap sites along the bainite interface crack path. IHAC is eliminated below a critical C, and thus above a critical temperature due to H detrapping. The relationship between KIH and C is predicted from a decohesion-based micromechanics model. Similitude provides the basis to predict a minimum pressurization temperature for pressure vessel operation without IHAC.

  • Introduction
  • Experimental Procedure
  • Results
  • Analysis
  • Discussion
  • Conclusions
  • Acknowledgements
  • References

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