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Supplementary data to the peer-reviewed article: Results Point energy dispersive spectroscopy Energy dispersive spectroscopy determined various surface regions and structures. In this analysis, the data were accumulated at the acceleration voltage of 11 kV. A representative group is visualized in the Figure S1 and the abundance is summarized below in Figure S2. The roughness of the surface plays a role mainly at lower temperatures as demonstrated at 550 °C. On the other hand, the differences at 1000 °C become less pronounced. All the samples are composed of similar structures but remained distinct in size distribution of grown crystal and the homogeneity across the surface. To be pointed out, a region around LOF defects (ground sample) is not clearly composed of crystallites but rather as a thick porous layer of Fe. In Figures S1 and S2, the point EDS analysis and the plotted composition is shown. The points represents following positions and structures: P1 represents composition of petal shaped particles, P2 represents plain surface on ground sample, P3 shows shade spot on polished sample, P4 showed ball-like crystal and P5 represents octahedral crystal composition on as-prepared sample, P6 represents the area of iron island, P7 represents smaller octahedral crystals and P8 represents plane surface of ground sample, P9 represents plain surface of polished sample, P10 represents shows small octahedral crystals and P11 shows greater octahedral crystals. 550 °C (36 h) 500 µm 500 µm 500 µm 20 µm 20 µm 20 µm 20 µm 500 µm 20 µm 20 µm 50 µm 500 µm 1000 °C (36 h) 20 µm 500 µm 0 10 20 30 40 50 60 70 80 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 Abundance (%) Iron Manganese Chromium Nickel Molybdenum Figure S2: Summarization of the element composition for corresponding point of Figure S1 Figure S1: Determination of point EDS analysis positions in oxidized 316L samples
EDS mapping Figure S3: EDS mapping of as-prepared 316L sample annealed at 1000 °C Figure S5: EDS mapping of polished 316L sample annealed at 1000 °C Figure S4: EDS mapping of ground 316L sample annealed at 1000 °C
X-ray diffraction See the list of used files from the Crystallographic open database in Table S1. Table S1: List of files used in XRD analysis Phase COD number Cr2MnO4 9012051 Cr2O3 9008095 Fe2O3 9015065 Fe3O4 9002322 γ-Fe 9008469 α-Fe 9013463 Conversion X-ray Mössbauer spectroscopy Conversion X-ray Mössbauer spectroscopy (CXMS) was used to determine the changes in greater depth of the studied samples. The expected depth of CXMS is similar to the X-ray diffraction penetration depth, e.g. ~30 µm. Additionally, CXMS is only sensitive to the Fe-containing structures. The presence of FCC-austenite was confirmed. On the other hand, any iron oxide was not determined by this method, indicating only surface changes that are visible by CEMS. Therefore, the spectrum in Figure S6 shows only a broad singlet near 0 mm/s which is a typical for γ-Fe. The isomer shift of -0,11(1) mm/s was determined in all measured spectra and summarized in Table S2. The width of the peak indicates possible quadrupole splitting due to the presence of alloying elements as discussed in the study. In addition, a decrease of the Mössbauer effect can be observed. Several factors can influence such reduction: increased photoelectron dispersion with increasing roughness of the surface in the geometry of our type of spectrometer, increased content of alloying elements and phases at the surface followed by a slight decrease in Mössbauer effect. Figure S6: Conversion X-ray Mössbauer spectra of the AM 316L samples.
Table S2: Hyperfine parameters of the conversion X-ray Mössbauer spectra of the AM 316L samples Sample Phase IS (mm/s) QS/ε (mm/s) FWHM (mm/s) As-prepared FCC-austenite -0.10 ± 0.01 0.17 ± 0.01 0.29 ± 0.01 As-prepared 550 °C FCC-austenite -0.10 ± 0.01 0.16 ± 0.01 0.27 ± 0.01 As-prepared 1000 °C FCC-austenite -0.10 ± 0.01 0.14 ± 0.01 0.29 ± 0.01 After grinding FCC-austenite -0.11 ± 0.01 0.16 ± 0.01 0.26 ± 0.01 After grinding 550 °C FCC-austenite -0.11 ± 0.01 0.17 ± 0.01 0.27 ± 0.01 After grinding 1000 °C FCC-austenite -0.12 ± 0.01 0.16 ± 0.01 0.28 ± 0.01 After polishing FCC-austenite -0.10 ± 0.01 0.16 ± 0.01 0.27 ± 0.01 After polishing 550 °C FCC-austenite -0.10 ± 0.01 0.16 ± 0.01 0.27 ± 0.01 After polishing 1000 °C FCC-austenite -0.12 ± 0.01 0.16 ± 0.01 0.28 ± 0.01
