Effects of high pressure hydrogen gas on the fatigue strength for long-term use in candidate materials for the fuel cell system

为了保证燃料电池系统材料在高压氢气环境下的长期疲劳安全性，有必要明确氢气进入材料的特性以及内部氢气和氢气对材料疲劳特性和疲劳机理的影响。(1)对SCM 435中氢含量的测量表明，等离子体带电样品中氢含量为0.25 ppm，是未带电样品的5倍。氢等离子体具有替代高压气氢环境的能力，但数据分散。需要讨论另一种等离子体产生方法或防止热演化的措施。(2)普通试样的疲劳寿命不能解释氢气环境的影响，因为氢气延长了疲劳裂纹的起始寿命，而缩短了疲劳裂纹的扩展寿命。(3) SUS304、SUS316L、SUS310S和A6061-T6材料的氢加速疲劳裂纹程度不同。(4)即使在氢气环境下，在疲劳裂纹扩展的一定范围内，滑移机理也是有效的。(5)认为传统的基于滑移的疲劳裂纹扩展评价方法是有效的，在评价方法中加入扩散速率的影响是下一个目标。

In order to ensure the safety of materials of a fuel cell system against long-term fatigue in high pressure hydrogen gas environment, it is necessary to clarify the characteristics of hydrogen entry into the material and the effects of internal hydrogen and hydrogen gas on the fatigue characteristics and the fatigue mechanisms.(1) Measurements of hydrogen content in SCM 435 show that a plasma-charged sample contains 0.25 ppm hydrogen, which is 5 times in non-charged sample. The hydrogen plasma has ability as an alternative of high- pressure gas hydrogen environment However, the data are spread. Discussion of another plasma generation method or measures against heat evolution is required.(2) Fatigue life of plain specimen cannot explain the effects of hydrogen gas environment, because hydrogen gas lengthen the fatigue crack initiation life, while shorten the fatigue crack propagation life.(3) Degree of fatigue crack acceleration by hydrogen is different among materials: SUS304, SUS316L, SUS310S and A6061-T6.(4) Slip-off mechanism is valid even in hydrogen gas environment in a certain range of fatigue crack growth.(5) It is considered that the traditional assessment technique for the fatigue crack growth based on slip-off is effective and addition of the effects of diffusion rate to the assessment technique is a next object.