Comprehensive study of deuterium-induced effects in austenitic stainless steel AISI 304L

The damaging impact of hydrogen on the austenitic stainless steel AISI 304 L was analysed. To this aim, samples were charged electrochemically with the hydrogen isotope deuterium ( ₂ H, D)and examined with time-of-flight secondary ion mass spectrometry (ToF-SIMS)and electron backscatter diffraction (EBSD). The fusion of the obtained chemical and structural information revealed local enrichment of deuterium in austenite, transformation into martensite, crack formation and severe roughening of the specimen surface. The results indicated that martensite was not only formed during charging but also during desorption and ToF-SIMS examinations. Furthermore, cross-sections of deuterium-charged samples revealed that in preferred deformation bands a γ→ε→α ^′ evolution is taking place. By means of microscopic analyses and carrier gas hot extraction (CGHE), it was found that the use of NaAsO ₂ as recombination poison decreased the uptake of hydrogen significantly and resulted in severe precipitation on the specimen surfaces. This is in contrast to the popular presumption that NaAsO ₂ enhances the uptake of hydrogen (and deuterium)during electrochemical charging by hampering its recombination from atoms to molecules.