Study of correlation between hydrogen-induced stress and hydrogen embrittlement

A X80 pipeline steel loaded over yield is unloaded and charged with hydrogen. The yield strength of the charged specimen loaded in air is lower than the flow stress before unloading, and the difference is defined as the hydrogen-induced stress, which can be added to the external stress to enhance the plastic deformation. The hydrogen-induced stress, σad, increases linearly with increasing hydrogen concentration C0, i.e., σad=−14.1+3.89C0. Fracture stress at slow strain rate tests during dynamic hydrogen charging increases also linearly with increasing hydrogen concentration, i.e. σF(H)=675−6.1C0. Threshold stress of hydrogen-induced cracking (HIC) during dynamic hydrogen charging under constant stress decreases linearly with increasing the logarithm of hydrogen concentration, i.e., σHIC=669−124 ln C0.