Relationship between hydrogen concentration and mechanical properties of 5Ni-16Cr-Mo steel

Abstract

The qualitative relationship between hydrogen concentration and notch tensile strength has been investigated for 5Ni-16Cr-Mo steel with different strength. The notch tensile strength was determined by means of slow strain rate test (SSRT) on circumferentially notched round bar specimens with the notch root radius of 0.15 mm after hydrogen charging. Meanwhile, the hydrogen diffusion behaviors of various strength steel were studied by thermal desorption spectroscopy (TDS) analysis. The SSRT results show that the T460 steel has higher susceptibility of hydrogen embrittlement in contrast with T520 steel. The activation energies and microstructure indicate that the dislocations and interfaces of martensitic laths are hydrogen traps in 5Ni-16Cr-Mo steel. By SSRT, the elastic limit of charged specimen loaded in air is higher than the flow stress without hydrogen charging before unloading, while the difference is defined as hydrogen-induced stress. The value of hydrogen-induced stress σ* increases linearly with hydrogen concentration: σ*=−0.622+2.015C0. The finite element analysis results of stress distributions near the notch tip have shown that the maximum principal stress increases with the notch root radius decreasing.