Mechanism of Hydrogen Embrittlement of Austenitic Steels (original) (raw)

Three main hypotheses of hydrogen embrittlement (HE) of austenitic steels are discussed based on the studies of the interatomic interactions, hydrogen-induced phase transformations and dislocations properties. Measurements of electron spin resonance and ab initio calculations of the electron structure witness that the concentration of conduction electrons increases due to hydrogen, which enhances the metallic character of interatomic bonds. The hypothesis of brittle hydrogen-induced phases is disproved by the studies of the silicon-alloyed steels: the silicon-caused increase in the fraction of the εH martensite is accompanied by the decrease of HE. Studies of strain-dependent internal friction have shown the hydrogen-caused decrease in the start stress of microplasticity and increase in the velocity of dislocations in accordance with HELP hypothesis. A mechanism of HELP is proposed based on the hydrogencaused enhancement of the metallic character of interatomic bonds, which results ...