Fatigue. Effect of Hydrogen Trapped by Inclusions on Ultra-Long Life Fatigue Failure of Bearing Steel.
Fatigue. Effect of Hydrogen Trapped by Inclusions on Ultra-Long Life Fatigue Failure of Bearing Steel.
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疲劳。
DOI：
10.2472/jsms.50.1068
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
K. Takai
中科院分区：
文献类型：
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作者：
Y. Murakami;N. N. Yokoyama;K. Takai
研究了轴承钢JISSUJ 2在N>107范围内的超高周疲劳破坏机理。特别关注热处理轴承钢（样品QT）断裂起源（表面下非金属夹杂物）附近的断裂形态。在光学显微镜观察期间，特定形态看起来较暗。具有Nf=105量级的短疲劳寿命的试样没有这样的暗区，ODA（光学暗区）。为了研究非金属夹杂物捕获的氢对疲劳性能的影响，制备了在真空中热处理然后淬火和回火的试样（试样VQ）。样品VQ含有0.07ppm氢，而常规样品QT含有0.80ppm氢。VQ样本的ODA略小于QT样本。通过二次离子质谱仪在样品QT和样品VQ的断裂起源处的夹杂物周围检测到氢。因此，ODA的形成与非金属夹杂物捕获的氢密切相关。根据夹杂物的原始尺寸，通过107次循环定义的疲劳极限，通过面积参数模型估算的疲劳极限为-10%不保守。将ODA的大小引入到疲劳极限的估算中，得到了不受氢影响的小裂纹机械疲劳门槛值。本文还讨论了双S-N曲线的形成机理。
The mechanism for fatigue failure in extremely high cycle fatigue in the regime of N>107 is studied on a bearing steel, JIS SUJ2. Special focus was given to the fracture morphology in the vicinity of fracture origin (subsurface nonmetallic inclusion) of a heat treated bearing steel (Specimen QT). The particular morphology looks dark during optical microscopic observation. Specimens with short fatigue life of the order of Nf=105 did not have such a dark area, ODA (optically dark area). To investigate the influence of the hydrogen trapped by nonmetallic inclusions on fatigue properties, specimens heat treated in a vacuum followed by quenching and tempering (Specimen VQ) were prepared. Specimens VQ contained 0.07ppm hydrogen as compared to 0.80ppm hydrogen for conventional Specimens QT. Specimens VQ had a slightly smaller ODA than Specimens QT. Hydrogen was detected by a Secondary Ion Mass Spectrometer around the inclusion at fracture origin of Specimens QT and Specimens VQ. Thus, it can be concluded that the formation of ODA is closely related to hydrogen trapped by nonmetallic inclusions. Estimations of fatigue limit by the √area parameter model based on the original size of inclusions for fatigue limit defined for 107 cycles are -10% unconservative. Considering the size of ODA into fatigue limit estimation, the √area parameter model can predict the mechanical fatigue threshold for small cracks without influence of hydrogen. The mechanism of duplex S-N curve is also discussed.