Abstract
The role of martensitic phase transitions in the embrittlement of stainless steels by hydrogen has been one of persistent controversial theme studied during recent years. The unresolved question, concerns the role of hydrogen in hydrogen induced phase transformation of the γ(fcc) austenite to α‘(bcc) and ɛ (hcp) martensite phases in the fracture mechanisms. The purpose of this study is to report the results of a TEM analysis of martensitic phase transitions under conditions of high hydrogen fugacities such as cathodic polarization in the absence of any externally applied stress.The results demonstrate the appearance of hydrogen induced ɛ-phase in 316L steel (Fig. 1(b)). No evidence of the appearance of α'-martensite phase after hydrogen charging was found within the grains, however, α'-martensite was found in front of the crack tip and along the crack surfaces as a very fine-grained polycrystalline structure (Fig. 1(c)).
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