Dynamics of Defect Accumulation During Hydrogen Charge of Stainless Steel

The data on the influence of hydrogen concentration in stainless steel 316 upon defect formation and defect accumulation during hydrogen electrolytic charge from LiOH+H2O solution are presented. The regularities of surface damage in dependence on electrolysis time at current densities in a range 0,5-1 A/cm2 was studied. At a hydrogen charge of less than 1 hour and current densities up to 1 A/cm2 surface erosion is not detected. At a charging time of three hours the following modifications of the surface were found: a) detection of borders grains of metal; b) a buckling of separate areas of the surface; c) flacking of metal plates of ungeometrical in dimension up to 100 jm. The dynamics of defects accumulation at depths from 0 up to 150 jm have been studied by the positron annihilation method. It is revealed that the average value of positron lifetime slowly varies depending on hydrogen concentration. The two-component decomposing of a spectrum of positron lifetime has shown a low intensity of a long-lived component conforming to the presence of large-size defects. It testifies that lattice of stainless steel is stable to implanted hydrogen at a selected velocity of a hydrogen charging. The obtained results allow us to make the conclusion that a bulk destruction of metal grains does not occur. At the same time, the hydrogen is actively connecting with carbides on borders of grains, therefore there is exhibiting of borders grains. These outputs are confirmed by the method of thermo-waves microscopy. The destruction on grain borders may be made by a reaction of hydrogen with impurities, which are precipiate on borders, for example, with carbon.