Thermal desorption spectroscopy evaluation of hydrogen-induced damage and deformation-induced defects

Abstract

Thermal desorption spectroscopy (TDS) was performed on ultra-low carbon (ULC) steel with various degrees of hydrogen-induced damage and deformation-induced defects. First, the extent to which hydrogen-induced damage manifests itself in TDS measurements was evaluated. Application of multiple test conditions on cold deformed ULC steel with and without the presence of hydrogen-induced damage showed that such damage did not appear as a hydrogen signal on the TDS spectra. Second, interesting features observed on the TDS spectra of cold deformed ULC steel were further investigated by assessing the TDS spectra of recrystallised and annealed ULC steel. As such, the four peaks in the TDS spectra were linked to microstructural features: interstitial lattice positions, grain boundaries, dislocations and microvoids.

Hydrogen Trapping in Laser Powder Bed Fusion 316L Stainless Steel

“…The main desorption peak of L-PBF 316L SS presents a relatively low value of activation energy for hydrogen desorption, 28 ± 4 kJ/mol, implying the presence of a reversible trap. According to previously published works [28][29][30]39,[42][43][44][45], this trap can be ascribed to an elastic stress field around dislocation or second-phase particles (E a ~0-20 kJ/mol), or a dislocation core (E a ~20-35 kJ/mol). An additional peak is observed at higher temperatures and its activation energy was found to be 62 ± 5 kJ/mol.…”

“…Therefore, for a better understanding of the behavior of the material in a hydrogen environment, it is important to study the characteristics of hydrogen traps. While there are numerous studies regarding hydrogen trapping in conventionally produced ASS [28][29][30][31][32], to the best of our knowledge, there is a lack of information on this issue about L-PBF ASS.…”

The Potential of the Internal Friction Technique to Evaluate the Role of Vacancies and Dislocations in the Hydrogen Embrittlement of Steels

“…However, still some hydrogen desorbed even after annealing at higher temperatures and therefore the peak was linked to the combined action of vacancies and dislocations. Laureys et al [ 93 ] also identified vacancies as an active trapping site in a cold‐rolled ultralow‐carbon steel. However, in their case the trapping by vacancies resulted in a small distinct second peak at the high‐temperature side of the main peak, resulting from trapping by dislocations and grain boundaries.…”

“…Several studies on the trapping of hydrogen by vacancies in steel have been performed using TDS. [27,[91][92][93][94][95][96][97][98][99] Nagumo et al [91] observed a single desorption peak after tritium charging of a tensile-strained low-carbon (0.025 wt% C) steel and attributed it to trapping of tritium by vacancies. This was based on the introduction of the peak by cold work and rapid decrease of the peak upon annealing at low temperatures; i.e., annealing at 473 K did already result in a significant reduction of the amount of tritium desorbed.…”

“…Nevertheless, Nagumo et al [91,92] and Laureys et al [93] reported that the desorption of hydrogen from vacancies results from the annihilation of the vacancies themselves rather than detrapping from the defect site. Therefore, caution must be taken when determining the activation energy as this analysis is based on desorption from a stable trapping site.…”