Simulation of Hydrogen Thermal Desorption under Reversible Trapping by Lattice Defects

Abstract

The hydrogen thermal desorption of a martensitic steel has been simulated assuming lattice hydrogen diffusion under a local equilibrium with reversibly trapped hydrogen as the rate-determining process. The calculated desorption curves reproduced the observed shift of the peak temperature associated with the specimen thickness and the heating rate. The calculation method involves a combination of a defect density and a hydrogen/defect binding energy as parameters. The dependence of the peak temperature on the defect density and the binding energy has been quantitatively shown. Assignment of the lattice defect relevant to the desorption curves is discussed. A calculation that took into account the increase in the defect density yielded results consistent with the observed change in the desorption curves associated with plastic strain.KEY WORDS: thermal desorption analysis; hydrogen diffusion; lattice defect; hydrogen trap; hydrogen embrittlement.

Numerical Analysis of Influence of Hydrogen Charging Method on Thermal Desorption Spectra for Pre-strained High-Strength Steel

“…Since thermal desorption spectra depend on many factors such as binding energy and concentration of trap sites which characterize the hydrogen trap state, the heating rate, and the specimen size, the numerical simulation is also employed for examining sensitivity of desorption spectra to these factors. [19][20][21][22] …”

Modeling of Hydrogen Thermal Desorption Profile of Pure Iron and Eutectoid Steel

“…These analyses are reviewed in detail by Turnbull. 16) The McNabb and Foster's equation was also used for estimating the amount of defects trapping hydrogen. 20,21) In recent years, several papers 16,17) reported the simulation of hydrogen desorption profiles by directly solving the McNabb and Foster's equation or the equation based on the Oriani's local equilibrium theory and the sensitivity of the profiles to simulation parameters. All of these works considered hydrogen diffusion in materials to simulate desorption profiles.…”

“…He estimated the amount of trapping sites and binding energy between hydrogen and trapping sites as well as the hydrogen diffusion constant using his theory. In the analysis of hydrogen desorption profiles, some papers 10,11,15,16) adopted the equation of McNabb and Foster, and others 14,15,17) used the Oriani's theory. These analyses are reviewed in detail by Turnbull. 16) The McNabb and Foster's equation was also used for estimating the amount of defects trapping hydrogen.…”

“…Theoretical analyses [10][11][12][13][14][15][16][17] of the hydrogen desorption profiles have been reported for decades in order to evaluate the amount of defects in alloys. Most of the reports are based on the equation of McNabb and Foster 18) and/or the Oriani's local equilibrium theory.…”

Effect of Intergranular Ferrite on Hydrogen Delayed Fracture Resistance of Ultrahigh Strength Boron-added Steel

“…Equation (1) can be applied when the thermal detrapping from defects is the rate determining step in the whole evolution procedure, i.e., when hydrogen is trapped at strong and irreversible traps. 20) Moreover, it should be noticed that the martensitic steels have many kinds of trapping sites such as grain boundaries, dislocations, precipitates and point defects. Consequently, the hydrogen diffusion process might be affected by simultaneous effects of the different trapping sites and the apparent activation energy should be an averaged one of various traps.…”