Hydrogen permeation in metals as a function of stress, temperature and dissolved hydrogen concentration

Abstract

An investigation of the diffusion of electrolytic hydrogen through membranes of: (1) polycrystalline Armco iron; (2) single crystal Armcoiron; (3) zone refined iron; and (4) A.I.S.I. 4340 has been made. The temperature and stress dependence of the permeation rate through (1) and (4) was investigated, while (1) to (3) have been investigated under varying concentrations of hydrogen in the metal. From the results concerning Armco iron polycrystals and single crystals, and zone-refined iron it has been concluded that trace impurities and grain boundaries have negligible effects on the hydrogen permeation rate. Stress has been shown not to affect D , but it increases the solubility of hydrogen in the lattice. The D 0 and Δ H p value for α-iron and the stress dependence of the hydrogen solubility indicate that the rate-determining step in diffusion is the formation of a cavity (a dilated octahedral hole) to accommodate the diffusion hydrogen. Maxima observed in the relation of the rate of permeation to time were explained in terms of ‘blister´ formation; the temperature dependence of the critical hydrogen concentration necessary to form these blisters is in concordance with this hypothesis. The nucleation sites for such blisters are aggregates of dislocations. The mechanism proposed to explain the maxima in the permeation transients was used to rationalize the existing discrepancies in diffusion data found in the literature. It is suggested that the crack initiation site for stress corrosion cracking may be a highly localized density of dislocations, on a metal surface, generated by blister formation due to hydrogen.

Effect of microstructure and composition on hydrogen permeation in X70 pipeline steels

“…This prevents the attainment of stationary conditions and consequently affects the steady state permeation flux. This trend of the permeation transient decreasing with time was also observed by Beck et al [44], Amiot et al [45] and Iino et al [38] . Beck et al [44] attributed it to void nucleation at an aggregate of dislocations and Amiot et al [45] attributed it to the hydrogen flux loss through the breakage of surface blisters.…”

“…This trend of the permeation transient decreasing with time was also observed by Beck et al [44], Amiot et al [45] and Iino et al [38] . Beck et al [44] attributed it to void nucleation at an aggregate of dislocations and Amiot et al [45] attributed it to the hydrogen flux loss through the breakage of surface blisters. However, similar to the present results for all samples, Iino et al [38] did not observe any blisters.…”

Hydrogen Embrittlement of Gun Steel

“…24 The Diffusion Coefficient is sensitive to temperature and follows the Arhennius The plot pf these data was replotted on a well-known chart of hydrogen diffusivity by'Frank Co. 25 (Figure 19), and this plotted in the middle of the ferritic material zone which showed excellent correlation with the data determined by Beck et al…”

“…All specimens were weighed on a balance that measured one tenth of a milligram; actual weights were rounded to the nearest milligram. It was determined that times on the order of [16][17][18][19][20][21][22][23][24] hours were needed to accumulate sufficient hydrogen to cause embrittlement.…”

Corrosion in the Oil and Gas Industry: An Increasing Challenge for Materials

“…The effect of stresses on hydrogen solubility was first addressed by Beck et al 24 in pure iron and in AISI 4340 steel. Different relationships were proposed to express the effect of tensile stresses on solubility.…”