Effects of hydrogen on fatigue crack growth behavior of austenitic stainless steels

Hydrogen Embrittlement Mechanism in Fatigue of Austenitic Stainless Steels

“…Hydrogen was charged into specimens either by cathodic charging [36] or by exposure to high-pressure hydrogen gas. The high-pressure hydrogen gas exposure was carried out in 63 MPa hydrogen gas at 110°C for 91 hours.…”

“…It was confirmed that cutting disks from a specimen did not affect the hydrogen content of the disk sample. [36] Figure 2 shows the hydrogen desorption spectra for an uncharged type 316L specimen (curve A) and for a hydrogen-charged specimen (curve B). The height of the peak at around 300°C, which indicates diffusible hydrogen, shows an increase due to hydrogen charging.…”

“…The level of hydrogen content in ordinary heat-treated bcc metals is on the order of 0.01 wppm [34,35] and, in ordinary solution-treated austenitic stainless steels, [36] it is on the order of 2 to approximately 3 wppm. This level of hydrogen content in austenitic stainless steels has been considered to be normal, and is the amount of nondiffusible (irreversible) hydrogen.…”

“…On the other hand, since the hydrogen diffusion rates in austenitic stainless steels are on the order of 10 -4 those of bcc metals, [36,38,39] both diffusible and nondiffusible hydrogen remain in a material for a long time. However, here we have a mystery: why does a hydrogen level of 2 to approximately 3 wppm in solution-treated austenitic stainless steels not influence HE?…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The present authors have investigated microscopically the effect of hydrogen on fatigue crack growth behavior, including the measurement of the exact hydrogen content, in various materials such as low-carbon, Cr-Mo, and stainless steels. For example, particularly important phenomena found by the authors' fatigue studies (Murakami et al, [32,33] Uyama et al, [34,35] Kanezaki et al, [36] and Tanaka et al [37] ) are the localization of fatigue slip bands, strain-induced martensitic transformation in types 304, 316, and even 316L, and also strong frequency effects on fatigue crack growth rates. These unique phenomena observed in fatigue experiments are presumed to have an important correlation with the basic process of the HELP model proposed by Birnbaum et al [3][4][5] In this study, the load frequency effect of hydrogen on fatigue crack growth rates has been revealed to be a coupled phenomenon between fatigue crack growth rates and hydrogen diffusion rates to fatigue crack tips, i.e., the competition between the crack growth rate and the hydrogen diffusion rate.…”