About the Role of Chromium and Oxygen Ion Diffusion on the Growth Mechanism of Oxidation Films of the AISI 304 Austenitic Stainless Steel

Anisotropic ion diffusion in α-Cr2O3: an atomistic simulation study

“…The faster oxygen anion diffusion at high temperatures obtained in the simulations agrees with previous experimental measurements. 9,10 To quantify diffusional anisotropy in the ab-plane and along the c-axis, we define a relative diffusion ratio C, calculated as D ab /D 3d and D c /D 3d , where D ab and D c are diffusion coefficients in the ab-plane and along the c-axis, respectively, and D 3d is the 3d diffusion coefficient plotted in Fig. 2(a).…”

“…The transport of cations and anions specifically through a-Cr 2 O 3 has been experimentally measured [6][7][8][9][10][11][12][13] and simulated, [14][15][16] though to a degree far lower than would be expected given its technological importance. The experimental literature is more extensive, as tracer experiments of oxygen and cation transport have been performed by multiple groups.…”

“…Hagel experimentally found that anion diffusion is slower in a-Cr 2 O 3 compared to cation diffusion. 6 Sabioni et al studied the diffusion of oxygen, 7 manganese, 8 chromium, 9 and iron 10 through chromia polycrystals and thin films by secondary ion mass spectroscopy (SIMS), eventually finding that oxygen diffusivity is faster than that of chromium in a-Cr crystal structure with a c/a axis ratio of 2.74 over a very wide pressure range, 17 any application utilizing a-Cr 2 O 3 as a passivation layer, from near-vacuum to ultra-high pressure, should benefit from the same texture-based gains in transport resistance. Therefore, precise knowledge of the orientation-dependent transport rates determines whether this strategy can succeed.…”

Ion transport mechanisms in the passive film formed on 304L stainless steel studied by ToF-SIMS with 18O isotopic tracer

“…Measurements of ion transport mechanisms in the oxide film formed on Fe-Cr based alloys are limited, and mainly focused on the ion diffusivities in the oxide scales at high temperatures (above 700°C) [28][29][30][31][32][33]. These data were performed by depositing the isotopic markers ( 54 Cr and 57 Fe) on the oxidized surface of the alloy followed by diffusion annealing.…”

“…Lobnig et al [28] determined cation diffusivities in the oxide film on Fe-20Cr and Fe-20Cr-12Ni at 900°C. Sabioni et al [31][32][33] studied the ion diffusion in the oxide films grown on different alloys (AISI 304 austenitic stainless steel, AISI 439 ferritic stainless steel and a ferritic Fe-15Cr alloy), between 750°C and 900°C, in air, and the ion diffusivities in the oxide scales of these steels were calculated. Although these works provide values of ion diffusivity in the oxide film, they do not elucidate the ion transport processes during oxide growth.…”