Influence of Cyclic Loads on the Fracture Resistance of Pipe Steels and their Welded Joints in Hydrogen-Sulfide Media

It is shown that the high resistance of 20, 30KhMA, and 12Kh21N5T steels to hydrogen-sulfide stress corrosion cracking does not guarantee their high resistance to corrosion fatigue fracture in the NACE solution (wt.%): 5% NaCl + 0.5% CH3COOH + H2S saturated; pH 3–4, 20 ± 3°С. It is shown that the increase in the amplitude of asymmetric cycles causes a more significant decrease in the durability of these steels than the increase in the average value of stresses. We reveal a significant influence not only of hydrogen embrittlement but also of corrosive processes on the fracture of welded joints in the NACE solution. It is shown that this is caused by the growth of their microelectrochemical heterogeneity in the corrosion process, which promotes the localization of corrosive defects.