Influence of low pressure hydrogen on the mechanism of destruction of steel in petrochemical equipment

The article described studies of the consequences of hydrogen corrosion of the steel walls of a chemical reactor during operation. Service life is 100,000 h. The walls are made of steel 09G2S. They worked under external thermomechanical load at low pressure of a hydrogen-containing internal environment (0.05 MPa). A comparison was made of the data obtained during the study of samples cut from the walls of the reactor with the data obtained during testing of isolated, hydrogen-charged samples made of steel of the same grade. New data were obtained regarding the influence of hydrogen and external load on the mechanical properties, structural and chemical transformations of steels. The differences between operational hydrogen corrosion and the consequences of hydrogen charging and from numerous previously published results were the increase in the ductility of the metal after operational hydrogen degradation (it becomes higher than that of new samples made of steel of the same grade) and the formation of a brittle fracture of this metal at a sufficiently high the value of its impact strength. It was also discovered that with complete decarbonization of some microstructure elements during operation, observed under a microscope, the average carbon concentration does not change, carbon accumulates at the grain boundaries. Nothing similar is observed in hydrogen-charged samples. Assumptions have been made about possible mechanisms, chemical reactions, the structure of the carbon formed in this process and its effect on the mechanical properties of the metal.