ステンレス鋼 SUS304 の微小疲労き裂の進展下限界に及ぼす水素の影響

Abstract

For the safety use of hydrogen utilization systems, it is necessary to understand properly the effect of hydrogen on the fatigue properties of structural materials. In the present study, fatigue life tests of 304 stainless steel with small artificial defects were carried out under the presence of hydrogen; the tests in hydrogen gas environment and the tests using hydrogen-charged specimens, and the effect of hydrogen on the fatigue limit of the material was investigated by paying attention to the behavior of short fatigue cracks. As a result, the fatigue limit was not degraded in hydrogen gas environment, whereas there was slight degradation of fatigue life in short life regime (i.e. Nf < 105 ). On the other hand, fatigue limit of hydrogen-charged specimens was increased compared with that of non-charged specimens. It is noteworthy that non-propagating cracks existed in the unbroken specimens in all environmental conditions. As is well known, fatigue limit of steels with low or moderate strength is determined by the non-propagation limit of small fatigue cracks. Consequently, it was revealed that the fatigue limit of the specimens was determined by the arresting limit of fatigue cracks, which was not degraded in the tests in hydrogen gas as well as in the tests using hydrogen-charged specimen.