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Derivation of hydrogen trapping and detrapping kinetic constants in Ni-base alloy 600 through coupled experimental and numerical analysis

Abstract : Part of the hydrogen present in pressurized water reactor primary medium (dissolved hydrogen or hydrogen from the water) can be absorbed by the metallic structural components, for example the steam generator tubes, in contact with it. After absorption, H will diffuse across the material, interacting with the interstitial sites and microstructural heterogeneities present in the alloy. It may accumulate along these heterogeneities, or trap sites, which may lead to a local degradation of the alloy's mechanical properties. H-trap site interactions were studied by coupling experimental thermal desorption mass spectroscopy (TDS) and numerical analysis to derive complete sets of trapping and detrapping kinetic constants in nickel base alloy 600. Model materials in which an isolated trap site type exists, i.e. chromium carbides or dislocations, have been fabricated and were used to study specific H-trap site interactions. Then deuterium, an isotopic hydrogen tracer, was introduced into the specimens by electrochemical charging. After charging, specimens were transferred to the TDS system and subjected to a temperature ramp during which the deuterium desorption flux was continuously monitored. TDS approaches, involving prolonged room temperature or elevated temperature aging, were used to isolate a trapping contribution on the experimental spectra. A TDS spectrum which presents an isolated trapping contribution was fit using a numerical routine based upon the McNabb and Foster equations. This fitting procedure takes into consideration all experimental steps and conditions and extracts the pre-exponential constants and activation energies associated with trapping and detrapping of hydrogen/deuterium at the isolated trap site type. The validity of the derived kinetic constants is tested through the simulation of experimental TDS spectra obtained on the same material having been subjected to different experimental conditions. Using this coupled experimental and numerical approach, one of the first complete sets of hydrogen trapping and detrapping kinetic data has been derived for an industrial fcc material. Finally, using these results a kinetic analysis of the Oriani hypotheses and their domain of validity will be explored.
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Submitted on : Thursday, January 16, 2020 - 1:43:40 PM
Last modification on : Friday, June 5, 2020 - 1:24:02 PM

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  • HAL Id : cea-02442367, version 1

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C. Hurley, F. Martin, L. Marchetti, J. Chene, C. Blanc, et al.. Derivation of hydrogen trapping and detrapping kinetic constants in Ni-base alloy 600 through coupled experimental and numerical analysis. International Hydrogen Conference 2016, Sep 2016, National park Grand Teton, United States. ⟨cea-02442367⟩

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