Effect of grain size on the hydrogen-assisted cracking in duplex stainless steels

The embrittlement behavior of 2205 duplex stainless steels with two different grain sizes in 26 wt% NaCl (pH 2) under cathodic potential were investigated by slow strain rate testing. The electrochemical permeation technique was used to characterize the permeation rate and effective diffusivity of hydrogen. The results indicated that both the effective diffusivity and the susceptibility of hydrogen embrittlement were lower for the finer grain size specimen. Ultimate tensile strength (UTS) and uniform elongation (UEL) decrease linearly with decreasing logarithm of strain rate. The dependence of UTS and UEL on the logarithm of strain rate was higher for the finer grain specimen. The microstructural examination revealed that internal cracks resulted from hydrogen embrittlement of the ferrite phase under cathodic charging conditions were arrested by austenite in duplex stainless steels.