Hydrogen Trapping Behavior Research Articles

Delayed Fracture Using CSRT Method and Hydrogen Trapping Characteristics of V-bearing High Strength Steel

The delayed fracture characteristics of V-bearing steel were evaluated using the CSRT method, and the hydrogen trapping and de-trapping behavior was studied with the specimens hydrogen-charged and then held in air for up to 2.5 months.The CSRT tests were carried out at two test sites and nearly the same delayed fracture characteristics were obtained using the V-bearing steel. The fracture appearance changed from quasi-cleavage to inter-granular fracture with an increase of hydrogen content. The boundary hydrogen content of the fracture appearance change is around 4 mass ppm.The hydrogen charged in V-bearing steel was composed of diffusible one, which comes out in 24 h when held in air of 30°C and two kinds of (weakly and strongly) trapped ones. The strongly trapped hydrogen remained in specimen after 2.5 months held in air. By analyzing the thermal desorption profiles with Gaussian function, the peak temperatures of these hydrogen were 100°C, 167°C and 198°C, which corresponds to diffusible, weakly and strongly trapped hydrogen.The specimens hydrogen-charged more than 4 mass ppm were fractured in inter-granular mode. After held in air and the hydrogen content became less than 4 mass ppm the fracture mode changed to quasi-cleavage. Re-charging the hydrogen more than 4 mass ppm, the fracture mode became inter-granular again.

鋼中 Cu 析出物の水素トラップ挙動

The hydrogen trapping behavior at Cu precipitates was investigated in martensitic Fe-0.18%C-1.5%Mn-4.0%Cu steel having various precipitation conditions. A hydrogen desorption peak was observed around 373 K in all samples. Total amount of desorped hydrogen decreased first with aging period but increased later. The initial decrease has been attributed to the recovery of lattice defects, and the increase in the later stage to trapping at Cu precipitates. The amount of desorped hydrogen increased even after peak hardening. The crystal structure of Cu precipitates was observed by SR-XAFS to be basically bcc; however, indication of fcc structure was also observed. The intensity of fcc structure increases with aging time. This suggests that incoherency of matrix-precipitate interface increases with aging time especially after peak strength, and that hydrogen trapping is more pronounced at incoherent interface than coherent one at Cu precipitates. Since misfit strain of coherent Cu precipitate is smaller than other precipitates such as TiC, the ability of hydrogen trapping at coherent Cu precipitates is estimated to be small.

Thermal desorption spectroscopy (TDS)—Application in quantitative study of hydrogen evolution and trapping in crystalline and non-crystalline materials

Thermal desorption spectroscopy is a very sensitive and accurate technique for studying hydrogen's diffusion and trapping processes in crystalline and non-crystalline materials. The technique involves accurate measurement of the desorption rate of gas atoms, soluted or trapped in the material, while heating the sample at a known rate. This paper reviews the thermal desorption spectroscopy (TDS) applications in quantitative studies of hydrogen trapping and release behavior in different crystalline and non-crystalline materials. It begins with a brief overview of the physical nature of hydrogen trapping and continues with a discussion on the origins of interactions between a hydrogen atom and a trap site. Based on the simple analytical model of Lee and Lee, some examples of the assessment of comprehensive properties of hydrogen evolution and trapping in different crystalline and non-crystalline materials by means of TDS are shown and discussed in detail.

Quantitative analysis on hydrogen trapping of TiC particles in steel

The change in the hydrogen-trapping behavior of a TiC particle accompanying its coherent to incoherent interfacial-character transition in a 0.05C-0.20Ti-2.0Ni steel that was quenched and tempered in a partially protective argon atmosphere and in ultrahigh vacuum (UHV) has been studied by thermal desorption spectrometry (TDS). The results indicated that (semi)coherent TiC precipitates demonstrate distinctly different hydrogen-trapping features from that of incoherent TiC particles with respect to hydrogen capacity, interaction energy with hydrogen, locations available for hydrogen occupation, and the capability of hydrogen absorption from the environment. The broad (semi)coherent interface of the disc-shaped (semi)coherent TiC precipitate does not trap hydrogen during tempering in a partially protected argon atmosphere, but traps hydrogen during cathodic charging at room temperature. The semicoherent interface traps 1.3 atoms/nm2 of hydrogen at the core of the misfit dislocation with short-time charging (1 hour), which is characterized by a desorption activation energy of 55.8 kJ/mol. The side interface of the (semi)coherent TiC precipitate acts like the broad interface when the precipitate is small. As the precipitate grows, the side interface gradually loses its coherency and results in a simultaneous increase in the trapping activation energy and the binding energy. An increase in the trapping activation energy, i.e., the energy barrier for trapping, makes hydrogen trapping more difficult in cathodic charging at room temperature, while an increase in the binding energy enhances the capability of hydrogen absorption from the atmosphere during heat treatment. An incoherent TiC particle is not able to trap hydrogen during cathodic charging at room temperature due to its high energy barrier for trapping, but absorbs hydrogen during heat treatment at high temperatures. The amount of hydrogen that is trapped by incoherent TiC particles depends on their volume, which strongly indicates that incoherent TiC particles trap hydrogen within them rather than at the particle/matrix interface. Octahedral carbon vacancies are supposedly the hydrogen trap sites in incoherent TiC particles.

Hydrogen Trapping Behavior in Vanadium-added Steel

Hydrogen trapping and de-trapping behavior was investigated for steels with and without V. The de-trapping of hydrogen is very slow while the trapping presumably proceeds rapidly for steels containing VC precipitates. The activation energy for de-trapping is in the range of 33 to 35 kJ/mol. The trapped-hydrogen content and diffusible-hydrogen content in the steady state increase with increasing hydrogen entry rate into the steel. The density of hydrogen trapping sites decides the maximum trapped-hydrogen content; 9 ppm for 1 % V steel tempered at peak secondary hardening temperature. Analysis of hydrogen embrittlement cracking tests in terms of hydrogen contents such as the critical hydrogen content should be performed on the specimens with uniform hydrogen distribution and must consider the nature of hydrogen whether it is trapped or diffusible.

Embrittlement damage of low alloy Mn–V steel

This work describes the hydrogen embrittlement damage of tubing made from a commercial low alloy manganese steel containing vanadium. Hydrogen charging of steels was carried out in 0.5 M H 2SO 4 solution which contained 10 mg/l As 2O 3 for 2 h under static load. Fractography was carried out using a scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometry (EDXS). Normalizing the tubing increased the yield strength. Tubing normalized at 900 °C is more resistant to hydrogen embrittlement (HE) compared to that in the as-received condition. The improved behaviour of steels when normalized at 900 °C can be attributed to a fine ferrite-pearlite microstructure (mean area of pearlite colonies 2.5 times smaller than in the as-received condition) and a beneficial variation in hydrogen trapping behaviour. Initiation of fracture occurred at complex inclusion/matrix interfaces. The size of the inclusions that caused fracture was 2 to 5 μm.

Diffusion behaviour of hydrogen in nitrogen containing austenitic alloys

Electrochemical permeation technique and thermal desorption spectroscopy were used to evaluate the hydrogen diffusion, solubility, and trapping behaviour in nitrogen containing austenitic alloys. The hydrogen diffusion of all alloys obeyed Arrhenius relationships in the studied experimental temperature range. The apparent diffusion coefficients were determined and the relevant activation energies were estimated. Nitrogen at higher concentration (>0.38 wt.%) as well as chromium decrease the hydrogen diffusion whereas nickel has opposite effect. The thermal analysis of all alloys except Cr18Mn18N0.57 shows a main single peak at different heating rates indicating no significant hydrogen interaction with microstructural defects. The alloy Cr18Mn18N shows a shoulder in addition to the peak which is attributed to nitrogen–hydrogen interaction. The activation energy estimated from the thermal analysis is nearly equal to the activation energy for diffusion obtained from the Arrhenius plots of the corresponding alloys.

The effect of strain on the trapping of hydrogen at grain-boundary carbides in Ni-Cr-Fe alloys

The present work quantifies the role of plastic deformation on the hydrogen-trapping behavior within the material and at the carbides. Isothermal desorption spectroscopy and thermal desorption spectroscopy (TDS) were performed on unstrained and strained alloy 600 (Ni-15Cr-8Fe) and alloy 690 (Ni-30Cr-8Fe), in order to quantify the effect of strain on the trapping energy. The results show that the M23C8 carbides in alloy 690 were stronger traps than the M7C3 carbides in alloy 600. It was further shown that cold work tended to increase the binding energy of hydrogen to the trap sites associated with grain-boundary carbides, although this effect was small.

Hydrogen mobility in diamond studies using HI-ERDA microscopy

Hydrogen plays a significant role in the growth of diamond and in the determination of its physical, electrical and optical properties. However, despite this significance, the configuration, chemistry and behaviour of hydrogen in the diamond lattice is still not very well understood. In this work, the stability of a collimated hydrogen implant distribution, as well as the intrinsic hydrogen distribution in a single crystal natural type IIa diamond are studied by imaging with the micro-scanned Heavy-Ion Elastic Recoil Detection Analysis (μHI-ERDA) technique in three dimensions. To investigate possible trapping of hydrogen at vacancies a shallow pre-damaged layer was created between the implanted hydrogen distribution and the surface by collimated bombardment of the sample with 50 keV 12C ions. No evidence of migration of the implanted or the intrinsic hydrogen to the pre-damaged region was observed even after annealing at 1473 K. The stability of the implanted hydrogen indicates the deep trapping of this species within its own implanted range distribution. The results confirm similar measurements previously performed on a natural type Ia diamond as well as on a synthetic type Ib diamond. The current sample was exceptionally pure, enabling an extension of these measurements to a situation where the intrinsic hydrogen concentration, as well as the hydrogen trapping behaviour might be expected to be different. Our results suggest complex trap configurations for hydrogen in diamond, not necessarily associated with nitrogen related defects.

Two-region model for hydrogen trapping in and release from graphite

A new model has been developed for hydrogen retention and trapping in and release from graphite. Two different regions in the graphite with different hydrogen transport and trapping behaviors are distinguished, the bulk region within, and the surface region on graphite crystallites. The model incorporates new experimental results related to atom diffusion and recombination on inner surfaces. Recombination is explained from a fundamental viewpoint by linking it to diffusion using a classical expression. The model is applied to a number of reemission and thermal desorption experiments, in particular, the reemission of hydrogen atoms during irradiation with energetic hydrogen ions and the formation of HD during irradiation with H+ and D+ or during thermal desorption of graphite that was preimplanted with H+ and D+ ions with different energies.

Thermal analysis of hydrogen-charged austenitic and duplex stainless steels

Abstract Observations on the hydrogen trapping behaviour of 22Cr5Ni duplex austenitic-ferritic and AISI 304 austenitic stainless steels by a thermal analysis method are presented. After hydrogen cathodic charging at constant current density, in the range 30–3000 min, the analyses were carried out after a break period of 20 min and 1440 min, to remove in part the diffusible hydrogen. Hydrogen trapping phenomena in steel with dual phase structure and in fcc structure are related to different evolution rate peaks of outgassed hydrogen. The effects of cathodic charging on microstructure were observed metallographically.

The effect of the interface character of TiC particles on hydrogen trapping in steel

A model for hydrogen trapping of particle-matrix interface was suggested, in which the large driving force for such hydrogen trapping was associated with the lowering of interfacial free energy. The effects of the character of the precipitated TiC-matrix interface on the hydrogen trapping behavior in steel was studied by utilizing the hydrogen thermal analysis technique. Incoherent titanium carbides have a larger trap activation energy of hydrogen than semi-coherent ones. Although the particles are incoherent, the trap activation energy of hydrogen increases with increasing the precipitated particle size.

Hydrogen trapping behavior of spheroidized 1520 steel as a function of plastic strain

Hydrogen trapping behavior of spheroidized 1520 steel as a function of plastic strain