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Comparative Study of Embrittlement of Quenched and Tempered Steels in Hydrogen Environments


The study of steels which guarantee safety and reliability throughout their service life in hydrogen-rich environments has increased considerably in recent years. Their mechanical behavior in terms of hydrogen embrittlement is of utmost importance. This work aims to assess the effects of hydrogen on the tensile properties of quenched and tempered 42CrMo4 steels. Tensile tests were performed on smooth and notched specimens under different conditions: pre-charged in high pressure hydrogen gas, electrochemically pre-charged, and in-situ hydrogen charged in an acid aqueous medium. The influence of the charging methodology on the corresponding embrittlement indexes was assessed. The role of other test variables, such as the applied current density, the electrolyte composition, and the displacement rate was also studied. An important reduction of the strength was detected when notched specimens were subjected to in-situ charging. When the same tests were performed on smooth tensile specimens, the deformation results were reduced. This behavior is related to significant changes in the operative failure micromechanisms, from ductile (microvoids coalescence) in absence of hydrogen or under low hydrogen contents, to brittle (decohesion of martensite lath interfaces) under the most stringent conditions.

Funding source: The authors would like to thank the Spanish Ministry of Science, Innovation and Universities for the financial support and FPI grant received to carry out research project RTI2018- 096070-B-C31 (H2steel weld), and A. Zafra and G. Alvarez to the Ministry of Education and Culture of the Principality of Asturias for the Severo Ochoa grants PA-18-PF-BP17-038 and PA-20-PF-BP19-087.
Countries: Spain

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