Increase in the local yield stress near surface of austenitic stainless steel due to invasion by hydrogen

In order to determine the effect of hydrogen on the local yield stress near the surface of austenitic stainless steel, an indentation test combined with inverse problem analysis was employed. For austenitic stainless steel, the indentation test is an effective method since the hydrogen is distributed near to the surface because of its high solubility and low diffusion coefficient. Although uniaxial tensile tests can also provide useful data, greater variations in the mechanical properties due to the presence of hydrogen can be detected through indentation tests. In this study, Secondary Ion Mass Spectrometry (SIMS) was used to measure hydrogen depth profiles in order to establish the relationships between the hydrogen absorption depth and the effects due to hydrogen evaluated using the indentation test. The results showed that the yield stress doubled due to hydrogen absorption and then reverted to its initial state due to hydrogen desorption at room temperature. Also, hardening due to the presence of hydrogen, which was determined using an indentation test, was found to be dependent on the relationship between the plastic deformation depth and the hydrogen absorption depth.