Investigation of local hydrogen distribution around fatigue crack tip on a type 304 stainless steel with secondary ion mass spectrometry and the hydrogen micro-print technique

In order to establish an appropriate method for measuring the local hydrogen content distribution around a fatigue crack tip in austenitic stainless steels, secondary ion mass spectrometry (SIMS) and the hydrogen micro-print technique (HMPT) were applied to a fatigue crack in a type 304 stainless steel tested in a hydrogen gas environment. The main results obtained in this study are as follows. In the SIMS method, there is a measurement error based on the edge effect regarding hydrogen in water vapor on the fatigue crack surface, though it is visualized that a high content of hydrogen exists in the plastic zone at a fatigue crack tip propagated in hydrogen, compared to that on a smooth area fatigued in hydrogen. On the other hand, this hydrogen in the plastic zone is difficult to detect with HMPT. In this case, this is attributed to the difficulty for hydrogen atoms to be emitted from the sample. To detect the hydrogen, it is necessary to sputter atoms forcibly. In addition, it is understood that to analyze the local hydrogen distribution around a fatigue crack tip with SIMS not only qualitatively but also quantitatively, reduction of the error based on the edge effect is necessary.