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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.
fatique strength, high strength steels, hydrogen embrittlement, ultrasonic fatigue, thermal desorption analysis of hydrogen, electrochemical hydrogen permeation method
R&D Engineer, NTN Corporation, Iwata,
R&D Engineer, NTN Corporation, Kuwana,