Hydrogen-induced defects of AISI 316 stainless steel studied by variable energy Doppler broadening energy spectra

Abstract

PACS 62.20.Fe, 78.70.Bj Hydrogen-induced defects of AISI 316 stainless steel were systemically investigated by measuring variable energy Doppler broadening energy spectra (DBES) of positron annihilation. Defect profiles of the S-parameter from DBES as a function of positron incident energy up to 30 keV (i.e. ∼1 µm depth) were analyzed. Experimental results showed that hydrogen damage between the surface and the bulk has a significant variation with depth, and strongly depends on the condition of hydrogen charging, i.e. current density and charging time. It has been suggested that the increase in the S-parameter near the surface after hydrogen charging mainly comes from the formation of hydrogen damage (voids); however, the increase in the S-parameter in the bulk after hydrogen charging mainly comes from the production of structural defects (dislocations). Defect densities induced due to hydrogen charging in some cases (e.g. dislocation density in the bulk) were estimated based on a simple trapping model.

Hydrogen‐damaged defects near the surface in heavily deformed iron and steels investigated by slow positron annihilation spectroscopy

“…Similarly to the result of deformed samples, it is also interesting to observe the similar variation of S and value for all three kinds of deformed and hydrogen-damaged samples. S-parameter near the surface in deformed and hydrogendamaged samples is much larger than in samples without hydrogen-damaged samples, but S-parameter in the bulk remain unchanged before and after hydrogen charging, which is evdently different from the results of annealed samples [6][7][8]. For annealed samples, hydrogen induced defects between the surface and the bulk has a significant variation with depth, and strongly depends on the condition of hydrogencharging, i.e.…”

“…3. Our previous work [6] indicated that S-parameter remained unchanged when hydrogen-charged samples in annealed 304 and 316 steel were placed in a vacuum chamber for 5 days, but S-parameter near the surface decreased if hydrogen-charged samples were exposed to air for 5 days. This indicated that a thin oxide film was formed on the external surface after 30 days exposure.…”

“…Recently, Wu et al [6][7][8] studied hydrogeninduced defects and hydrogen damage by PAL and slow positron beam in annealed AISI 304 and 316 stainless steels, and indicated that hydrogen damage starting from surface to the bulk had a significant difference with depth, and strongly depends on the condition of hydrogen-charging. In this paper, we further report hydrogen-damaged defects of heavily deformed iron, AISI 304-, and 316-stainless steels by measuring Doppler broadening energy spectra (DBES) of positron annihilation radiation.…”

Positron Annihilation in Corroded Steels St20 and St3S

“…As Pajak et al proved [15,16], and also Wu and Jean [17], electrolytic hydrogenation of samples of metals and steel causes, on the one hand, trapping hydrogen atoms in lattice defects, due to which they become inaccessible for positrons, on the other one -causes formation of new defects such as monovacancies, dislocations and multivacancy clusters. We assumed that during electrolytic hydrogenation of samples of steel, there form, in their near-the-surface layers, defects whose presence influences the kinetics and mechanism of corrosion at a later stage.…”

“…It has also been known for many years that electrolytic hydrogenation of iron and steel causes new defects to form in the sample [15][16][17]. We think that hydrogen that penetrates into the metal forms given defects in the near-the-surface layer.…”