The design of liquid hydrogen tanks requires a thorough assesment of the factors influencing fatigue resistance at cryogenic temperatures of austenitic stainless steel alloys  in hydrogen environments.

In these materials, Hydrogen Embrittlement (HE) is commonly associated with a reduction in tensile ductility, with a peak embrittlement occurring around -80°C and diminishing at very low temperatures. This study aims to evaluate the high-cycle fatigue resistance of two austenitic stainless steel grades, namelty 304L and 316L, in a hydrogen environment over a temperature range of -120°C to 100°C with a stress ratio R=0.1. A special focus is placed on the individual effects of hydrogen diffusion, as well as strain-induced phase transformations, especially at low temperature. The role of internal hydrogen is also considered; for this purpose, samples were pre-charged with hydrogen gas at 350°C for 96 hours under a pressure of 15 bar, and then tested in fatigue in air and in hydrogen gas. The quantity of hydrogen retained in the materials is evaluated through the use of thermal desorption spectroscopy (TDS).

The results on the coupled influence of temperature and hydrogen on fatigue strength are presented in two parts. The results indicate that the fatigue life is longer when the temperature is lower, given the same stress amplitude. It comes out that the exposure to hydrogen gas has no significant effect on the ratcheting deformation observed under a stress ratio of 0.1, but it does affect fatigue life at higher stress levels when exposed to a hydrogen pressure of 1.5 MPa. The influence of external hydrogen appears to be more pronounced than that of internal hydrogen.

The impact of martensitic transformation at low temperatures on fatigue strength in the presence of hydrogen is also examined. Finally a correlation between crack initiation and ratcheting behavior is proposed.