Fatigue threshold as a parameter of hightemperature hydrogen degradation of low-alloy steels used for power and petrochemical equipment

摘要

In order to substantiate the choice of workability factor for the evaluation of mechanicalstate of metal, we have compared various mechanical factors by their sensitivity to hightemperaturehydrogen degradation. Just local factors of fracture mechanics (such as fracturetoughness and threshold Stress Intensity Factor) were found to be the most sensitive to suchchanges, and therefore subsequently Stress Intensity Factor was used as indicator of mechanicalstate of the metal with different degradation level. The inversion of effect of hydrogen, absorbedby degraded metal, on its effective threshold of cyclic crack resistance depending on number ofthermocycles in hydrogen and exploitation time has been revealed. The metal state when negativeeffect of absorbed hydrogen on its effective threshold appears is suggested to be limiting.