In rolling contact fatigue, hydrogen is believed to contribute to early flaking failures under some conditions. Hydrogen diffuses quickly in steels, even at room temperature, thus resulting in its dissipation into the surrounding atmosphere. This condition presents a uniquely difficult challenge for evaluating the intrinsic fatigue properties related to hydrogen embrittlement. In order to compensate for this, we employed ultrasonic fatigue testing at a loading frequency of 20 kHz, because a high loading frequency offsets the rapid hydrogen loss. In this report, the fatigue properties of hydrogen pre-charged JIS-SUJ2 (SAE52100 equivalent) were assessed. The amount of hydrogen was quantitatively measured by thermal desorption analysis. The diffusion coefficient of hydrogen was determined via electrochemical hydrogen permeation testing. These results indicate that the magnitude of fatigue strength reduction is directly proportional to the diffusible hydrogen content. Included with this report is our proposed method for evaluating fatigue strength related to hydrogen embrittlement.

A remarkable difference in thermal desorption spectra of hydrogen obtained from pre-strained highstrength steel specimens which were charged with hydrogen by two different methods was observed. One charging method is by immersion in NH4SCN solution and the other is by cyclic corrosion tests. In order to understand the difference, we simulated numerically thermal hydrogen spectra of the pre-strained high-strength steel. As a result, it was found that the difference of desorption spectra results from the difference of initial hydrogen states which is caused by the amount of charged hydrogen. It was also found that the desorption spectrum in the case of cyclic corrosion test is more sensitive to the initial hydrogen state than that of the immersion case because the amount of charged hydrogen in the former is not as enough as that in the latter.

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