Influence of compressed hydrogen on the fatigue behavior of a ferritic stainless steel

Metallic materials, e.g. used for fuel cell components, have to show a high corrosion fatigue resistance against gaseous hydrogen in context of hydrogen susceptibility. This work shows the influence of gaseous hydrogen on the fatigue behavior of a ferritic stainless steel in the low cycle (LCF) and the high cycle fatigue regime. Therefore, strain-controlled and load-controlled fatigue tests are conducted in gaseous hydrogen under pressure and as a reference in ambient air. The evaluation of the test results focuses on the determination of the stress-strain behavior and the cyclic softening and hardening behavior. Based on this evaluation the investigated ferritic stainless steel shows a strong reduction in lifetime at high strain amplitudes under gaseous hydrogen compared to the reference investigations in air. The evaluation of the stress-strain behavior in form of the cyclic stress-strain curve and the cyclic deformation curves showed no significant difference, instead. However, a lifetime reducing effect of the hydrogen can be observed. On the other hand, it can be shown by the help of the load-controlled fatigue tests that the damaging influence of the hydrogen decreases with the reduction of the load level. If the local stress or strain falls below a level where only elastic material behavior can be assumed, the determined fatigue strength under air and hydrogen coincide. In this case, the generation of dislocation is drastically reduced, lowering the damaging influence of on the investigated material.