SIMS analysis on austenitic stainless steel: The influence of type of oxide surface layer on hydrogen embrittlement

Abstract

The surface oxide layer on nine different types of solution-annealed austenitic stainless steel (ASS) was evaluated by Secondary Ion Mass Spectrometry (SIMS). Tensile tests were conducted at 25 degrees C and -50 degrees C in hydrogen at 40 MPa and in air at atmospheric pressure. Relative reduction of area (RRA) was calculated accordingly. Additionally the martensite transformation curves were measured in air at -50 degrees C to evaluate the probability of the formation of alpha' martensite nuclei. A linear relationship between RRA and the calculated probability of the nucleation of alpha' martensite nuclei was found on samples represented by the following three oxides types; (a) thick oxide, (b) decaying sub-surface oxide and (c) thin surface oxides. However, type (d) with high constant oxide level down to 60 nm depth does not follow the trend. The observed variation of the oxide layer is linked to the variability of tensile test results. (C) 2013 Elsevier B.V. All rights reserved.