Deformation aging of steels results generally in embrittlement. An assumption of the possibility of occurrence of deformation ageing of steels at the microscale due to internal stresses induced by hydrogen under long-term operation was made. It was substantiated experimentally using the low-alloy pipe steel subjected to different treatment with and without preliminary electrolytical hydrogen charging and low-temperature tempering. The basic mechanical properties of the steel, impact strength, fracture toughness, and resistance to stress corrosion cracking were assessed. It was revealed that low-temperature tempering did not affect the mechanical behavior of the steel. However, the steel subjected to the procedure of combining preliminary hydrogen charging with subsequent low-temperature tempering was characterized by a significant decrease in fracture toughness and resistance to stress corrosion cracking. Hydrogen had an impact on the embrittlement of the steel through the strain aging at local sites being preferable for hydrogen diffusion.
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