Chemical characterisation of scale formation of high manganese steels (Fe-Mn23-C0.6) on the sub-micrometre scale: A challenge for EPMA

Abstract

Fe-23Mn-0.6C steel oxidation in the initial state of annealing in synthetic air and an Ar / 4 % H 2 / 7 % H 2O atmosphere (600, 800 and 1000°C for 20 min) was investigated. The chemical structure of the oxide scale and near-surface region of the oxidized sheet was characterized by electron probe microanalysis (EPMA). The results were correlated with the crystallographic structure of the sheet measured by electron backscatter diffraction (EBSD). Special preparations techniques i.e., focussed ion beam (FIB) milling and cross-section polishing by Ar-ions were applied to satisfy the requirements of quantitative X-ray and EBSD analyses. Moreover, carbon concentration profiles were measured on samples prepared by ion beam techniques and the conventional way with lubricants and polishing materials. Finally, a model of the near-surface region was derived by combining the results of quantitative analysis and X-ray mappings and was compared with thermodynamic calculations.