Effects of hydrogen on the properties of iron and steel

Hydrogen-Vacancy Interactions in Fe-C Alloys

“…Moreover, these observations inform macroscopic concerns of hydrogen damage by indicating conditions under which mechanisms of primary degradation by internal hydrogen pressure buildup [4] (i.e., H accumulation) are viable. For such processes to occur, the local vacancy concentration must be such that molecular hydrogen formation is favored, such as in the neighborhood of a microvoid or microcrack [4]. In other words, the point defect composition must be within the H II dominance zone in Fig.…”

“…DOI: 10.1103/PhysRevLett.103.085501 PACS numbers: 61.72.JÀ, 61.72.SÀ, 71.15.Mb, 71.15.Nc In the past few decades, a variety of fundamentally new phenomena has been observed in metals and their alloys under hydrogen-rich conditions, such as large volume contractions in body-centered cubic (bcc) -Fe [1,2], and the enhancement of diffusion at metal-metal junctions [3]. Furthermore, the well-known problem of hydrogeninduced degradation of the mechanical properties of metals has had significant impact in Fe-rich alloys such as hardened steels that suffer severe embrittlement [4,5]. Experimental and theoretical evidence [1][2][3][4][5][6][7] suggests that one unifying theme behind these hydrogen-mediated effects is the strong interaction between hydrogen impurities and other point defects in the material, and the subsequent microstructural changes that occur as a result of that interaction.…”

“…Furthermore, the well-known problem of hydrogeninduced degradation of the mechanical properties of metals has had significant impact in Fe-rich alloys such as hardened steels that suffer severe embrittlement [4,5]. Experimental and theoretical evidence [1][2][3][4][5][6][7] suggests that one unifying theme behind these hydrogen-mediated effects is the strong interaction between hydrogen impurities and other point defects in the material, and the subsequent microstructural changes that occur as a result of that interaction. Although a rich experimental literature detailing macroscopic effects exists, fundamental understanding of the interactions of hydrogen with point defect clusters (PDCs) in metals is limited.…”

“…However, as the number of solute atoms in the PDC grows, the presence of additional vacancies is required to promote hydrogen binding. Alternatively, appreciable lattice distortions in the form of extended defects, such as precipitate interfaces [4], can provide an analogous effect to that of vacancies in the bulk lattice by facilitating C-H binding. The combination of the two competing processes of hydrogen-carbon interactions (repulsion in the absence of vacancies but high affinity when mediated by vacancies) results in an effective decoupling of the Va x H z and Va x C y PDC populations; that is, vacancy-solute (Va-H and Va-C) interactions become the primary contributors to the binding processes.…”

Thermal Desorption Analysis of Hydrogen in Non-hydrogen-Charged Rolling Contact Fatigue-Tested 100Cr6 Steel

“…Traps can include inclusions, cracks, grain boundaries, carbides, microvoids, retained austenite and areas of local plastic deformation where the density of crystal defects (dislocations) is large and hydrogen binding with these crystal defects occurs [14,[16][17][18][19][20][21][22][23][24][25][26]. Traps can be split in terms of their desorption temperature and binding energies.…”