SIMS analysis of hydrogen content in near surface layers of AISI 316L SS after electrolytic polishing under different conditions

Abstract

Hydrogen concentration in AISI 316L stainless steel samples was monitored perpendicularly to the flat sample surface up to the depth of 0.8 μm, using secondary ion mass spectrometry (SIMS). Depth profile analysis was performed on the samples after electrolytic polishing under different conditions. Analyses were performed on SAJW-05 apparatus with quadrupole Balzers QMA-410 analyzer and Physical Electronics 06-350E ion gun. 5 keV Ar + primary ion beam of 100 μm diameter was scanned over 1 mm × 0.8 mm area. Positive (H +, C +, CH +, O +, Cr +, Fe +) and negative (H −, C −, CH −, O −, OH −, CrO −, FeO −) secondary ion emission was registered from central part of the scanned area (10% of area) during primary ion beam sputtering. Results of hydrogen depth profile analysis were compared for the samples after a conventional electrochemical polishing (EP), and magnetoelectropolishing (MEP). Both EP and MEP processes were carried out under the electrochemical conditions regarding also natural and forced convection. The steel samples taken of a hot-rolled sheet, as received (AR), and after abrasive polishing (MP), were used as a reference. Results show that the increased current density (up to 200 A/dm 2) and electrolyte stirring during electropolishing cause lowering of the hydrogen content in the samples, with the best result regarding hydrogen content decrease obtained on MEP200 sample. In fact, within the MEP process, characteristic with the self-contained electrolyte whirling, the contents of hydrogen are significantly decreased.