Visualization of the hydrogen desorption process from ferrite, pearlite, and graphite by secondary ion mass spectrometry

Abstract

The distribution and desorption processes of hydrogen and deuterium have been visualized by secondary ion mass spectrometry (SIMS). The present article deals with four principal points: (1) visualizing the hydrogen distribution, (2) visualizing the hydrogen desorption process from each metallurgical microstructure under various holding times at 25 ЊC, (3) visualizing the hydrogen desorption process during heating, and (4) determining the correspondence between desorption profiles and desorption sites. A spheroidal graphite cast iron specimen was prepared for visualizing hydrogen, since it consists of basic microstructures of steels such as ferrite and pearlite. Hydrogen and deuterium were occluded into the cast iron. The amount of hydrogen and the existing states of hydrogen in the cast iron were analyzed by thermal desorption spectrometry (TDS). The TDS analyses show that the hydrogen desorption has two peaks, namely, the low-and high-temperature peaks corresponding to trap activation energies of 21.6 and 105.8 kJ/mol, respectively. The SIMS analyses of the specimen cooled after heating to 100 ЊC, 200 ЊC, and 300 ЊC reveal that the hydrogen desorbs from the ferrite after heating to 100 ЊC, from the pearlite and the interfaces between the ferrite and the graphite after heating to 200 ЊC, and from the pearlite after heating to 300 ЊC. The graphite remains, trapping hydrogen after heating to 300 ЊC. On the basis of TDS and SIMS results, the relationship between the desorption profile and desorption sites was identified; that is, the low-temperature peak corresponds to ferrite, pearlite, and graphite/ferrite interfaces, while the high-temperature peak corresponds to graphite.

Micro-Portion Image Analysis of Light Elements in Fe–Cr Based Alloys by Time-of-Flight Secondary Ion Mass Spectrometry

“…25,26) Concerning steels samples, dynamic SIMS has been shown to be an effective method for detecting deuterium or hydrogen in different steels. [27][28][29][30][31][32] These results showed that deuterium or hydrogen is enriched in specific microstructures, although this enrichment depends on the species of steel. The dynamic SIMS has also been applied to observe the distribution of light elements such as boron and nitrogen in steels.…”

Effect of Hydrogen on Uniaxial Tensile Behaviors of a Ductile Cast Iron

“…The results indicate that most of hydrogen was stored in graphite and pearlite. Takai et al 5 showed that hydrogen was mainly segregated at graphite-ferrite interface and pearlite. Ogi et al 6 concluded that the reason why ferritic spheroidal graphite cast iron can store more hydrogen than ferritic steel is because graphite/matrix interface has a great capacity to store hydrogen.…”

Hydrogen Desorption Behavior of Pure Iron and Inconel 625 during Elastic and Plastic Deformation

“…Hiroki SHODA, 1) Hiroshi SUZUKI, 2),3) Kenichi TAKAI 2), 3) and Yukito HAGIHARA 2) 1) Formerly Graduate Student, Sophia University. Now at NSK Ltd., 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 Japan.…”

“…The trapping sites of this weakly trapped state are dislocations, vacancies, grain boundaries, cementite interfaces, and solid solution hydrogen in the lattice. [1][2][3][4] However, there is little agreement about the effects of trapping sites and how they cause hydrogen embrittlement. [5][6][7][8] The role of weakly trapped hydrogen or solid solution hydrogen diffusive at room temperature has been examined for Inconel 625 and pure iron.…”