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The locally occurring mechanisms of hydrogen embrittlement significantly influence
the fatigue behavior of a material, which was shown in previous research on two different AISI
300-series austenitic stainless steels with different austenite stabilities. In this preliminary work, an
enhanced fatigue crack growth as well as changes in crack initiation sites and morphology caused
by hydrogen were observed. To further analyze the results obtained in this previous research, in
the present work the local cyclic deformation behavior of the material volume was analyzed by
using cyclic indentation testing. Moreover, these results were correlated to the local dislocation
structures obtained with transmission electron microscopy (TEM) in the vicinity of fatigue cracks.
The cyclic indentation tests show a decreased cyclic hardening potential as well as an increased
dislocation mobility for the conditions precharged with hydrogen, which correlates to the TEM
analysis, revealing courser dislocation cells in the vicinity of the fatigue crack tip. Consequently,
the presented results indicate that the hydrogen enhanced localized plasticity (HELP) mechanism
leads to accelerated crack growth and change in crack morphology for the materials investigated. In
summary, the cyclic indentation tests show a high potential for an analysis of the effects of hydrogen
on the local cyclic deformation behavior.