The influence of the structural-mechanical state of the gas transit pipeline steel on the susceptibility to hydrogen embrittlement

Different modes of cathodic polarization of pipe steel specimens based on current density, which determines its moderate and intense hydrogen charging, are substantiated. The hydrogen embrittlement resistance of 17H1S steel in the as-delivered and post-operated states was determined by the change in plasticity depending on the hydrogen charging intensity and the direction of cutting the specimens relative to the pipe axis. Unexploited steel is not prone to hydrogen embrittlement under moderate hydrogen charging, while exploited steel shows this feature. The important role of non-metallic inclusions in the hydrogen embrittlement of steel, which depended on its structural-mechanical and hydrogen charging conditions, was determined using metallographic and fractographic analyses. Under moderate hydrogen charging intergranular embrittlement takes place while under intense mode transgranular embrittlement, the differences are due, obviously, to different mechanisms of transport of hydrogen absorbed by the metal.