Quantitative investigation of hydrogen-induced additive stress for high-strength steel

The flowing stress of a high-strength steel before unloading is different with the yield stress of the same sample extended in air after unloading and charging with hydrogen. The difference is the hydrogen-induced additive stress, which can help the external stress to enhance the plastic deformation. The hydrogen-induced additive stress, sigma(ad), induced through immered in a 3.5% NaCl solution with pH=4, corresponding to hydrogen concentration (mass fraction) of 3.05 x 10(-4)% increases linearly with the yield strength of the sample, e.g., sigma(ad)=0.14sigma(ys)-106.6. On the other hand, hydrogen-induced additive stress increases linearly with the logarithm of hydrogen concentration for the samples with the yield strengths of 900 MPa and 1050 MPa, i.e, sigma(ad)=-55.5+63.6 In C-0(sigma(ys)=900 MPa) and sigma(ad)=-23.5+64.2 ln C-0(sigma(ys)=1050 MPa). To sum up, the hydrogen-induced additive stress can be described as sigma(ad)=-260+0.226sigma(ys)+63.9 ln C-0.