オーステナイト系ステンレス鋼の低サイクル疲労におけるマルテンサイト変態に及ぼす水素の影響

抄録

Low-cycle fatigue tests and X-ray diffraction measurements were carried out using uncharged and hydrogen-charged specimens of austenitic stainless steel JIS-SUS316 in order to investigate effects of hydrogen on strain induced martensitic transformation in low-cycle fatigue tests. The specimens were polished with buff and introduced small artificial holes whose diameter was 100 μm and 300 μm. Low-cycle fatigue tests were carried out up to 100 cycles under reversed torsional loading and circular loading. The strain range was 1 %. After the fatigue tests, X-ray diffraction measurements were conducted in order to investigate the amount of martensitic phase. The experimental results showed that the equivalent stress range of the hydrogen-charged specimens increased, compared to the uncharged specimens. Hydrogen may have been promoted cyclic hardening. The amount of martensite of the uncharged and hydrogen-charged specimens increased in fatigue tests when the amount of martensite before the tests was less than 11 %. On the other hand, the amount of martensite of the uncharged and hydrogen-charged specimens decreased in fatigue tests when the amount of martensite before the tests was more than 11 %. The cause may be that surface polishing affected on strain-induced martensitic transformation. Therefore, it is necessary to consider the possibility that residual stress due to surface polishing may have affected the amount of martensite.