Role of grain boundaries in the diffusion of hydrogen in nickel base alloy 600: Study coupling thermal desorption mass spectroscopy with numerical simulation

Abstract

International audienceThe role grain boundaries play in the diffusion of hydrogen in polycrystalline alloys has long been debated. Some researchers have found that grain boundaries have an accelerating effect on the transport of hydrogen across a metal membrane, while others have stated this network of sites may slow the diffusion of hydrogen or have a mixed effect depending on grain size and orientation. Thermal desorption mass spectroscopy (TDS) was used to study the diffusion of deuterium, from 294 K to 550 K, in model single crystal and polycrystalline nickel base alloy, alloy 600, having a grain size of several tens of micrometers. Using a numerical routine, solving Fick's second law of diffusion, TDS spectra were fit or simulated. The derived diffusion constant parameters (D0 = (1.0 ± 0.5)·10−2 cm2 s−1 and ED = (45 ± 4) kJ mol−1) for the polycrystalline alloy adequately predict and simulate the deuterium desorption from the single crystal during TDS testing. Furthermore, in the temperature range and for the grain size studied no significant effect of grain boundaries on the diffusion of deuterium in alloy 600 was observed. Consequently, the measured diffusion parameters are representative of interstitial diffusion in the alloy

A Critical Review of Mg-Based Hydrogen Storage Materials Processed by Equal Channel Angular Pressing

“…When more H atoms are introduced, H atoms continue to occupy the lower energy sites and begin to pass through higher energy sites where the diffusion activation energy is lower. Calculations have proven that lower activation energy appears along grain boundaries, which means that grain boundaries can function as easy pathways for H atoms to diffuse into the bulk [49][50][51][52][53][54].…”

Isotopic tracing of hydrogen transport and trapping in nuclear materials

“…Moreover, according to the K r value (cf. §2a) and as illustrated in figure 6, in order to avoid misinterpretation of TDS spectra one has to check carefully the validity of the explicit and implicit assumptions on the boundaries conditions included in the model and to use a rigorous numerical simulation method [26].…”

“…SIMS profiling of deuterium as a function of successive isothermal heat treatments, coupled with TEM observations of the microstructure evolution, is another way to get some insight on H interactions with defects in metals. Such experiments have been conducted on alloy 690 first implanted with Ni + ions, then deuterated at room temperature, in order to study H interactions obtained for the same H charging conditions, on H desorption spectra from a model material [26]. Note that the occurrence of a second peak on some spectra has nothing to do with trapping effects [26].…”

“…Such experiments have been conducted on alloy 690 first implanted with Ni + ions, then deuterated at room temperature, in order to study H interactions obtained for the same H charging conditions, on H desorption spectra from a model material [26]. Note that the occurrence of a second peak on some spectra has nothing to do with trapping effects [26]. [27] suggesting that H-defects interactions can be operative in the working temperature range of PWR.…”

Numerical Interpretation of Hydrogen Thermal Desorption Spectra for Iron with Hydrogen-Enhanced Strain-Induced Vacancies

“…Understanding and interpretation of experimental thermal desorption spectra using a numerical model have been reported [17][18][19][20][21][22] . Although various kinds of models are employed in those reports, the models can broadly be classified mainly into three types [23] .…”