SIMS study on the surface chemistry of stainless steel AISI 304 cylindrical tensile test samples showing hydrogen embrittlement

The local surface chemistry of a low-Ni austenitic stainless steel AISI type 304 used for tensile testing in hydrogen atmosphere is characterized by secondary ion mass spectrometry (SIMS). A chemical map on cylindrical austenitic stainless steel samples can be obtained even after a tensile test. In an effort to obtain the proper chemical element distribution on the samples, the influence of contamination and sample orientation is discussed. An iron oxide on top of a chromium oxide layer is present and Si segregation at grain boundaries is detected. Oxides are judged to reduce the initial hydrogen attack but to be of minor importance for crack propagation during the embrittlement process.

Research highlights▶ The surface chemistry of AISI 304 was characterized by SIMS. ▶ A chemical map on cylindrical samples was obtained even after a tensile test. ▶ For a correct analysis, surface roughness and sample geometry had to be adjusted. ▶ A layered stacking of Fe- and Cr-oxide with a thickness of 9 nm was found. ▶ Si segregated at grain boundaries in a solution annealed sample thorough diffusion.