Diffusion of carbon in stainless steels

Carburization of Austenitic and Ferritic Steels in Carbon-Saturated Sodium: Preliminary Results on the Diffusion Coefficient of Carbon at 873 K

“…The resulting value of D app was 1.8 ± 0.3 9 10 -11 cm 2 s -1 . Standard deviation was calculated taking an average of three carbon profiles at 500 h and four carbon profiles at 1000 h. Calculated D app was in agreement with the values found by Meny [2] (D app = 2.0 9 10 -11 cm 2 s -1 ) and Thorley and Hobdell [13] (D app = 1.9 9 10 -11 cm 2 s -1 ) but lower than the one measured by Agarwala et al [14] (D app = 9.5 9 10 -11 cm 2 s -1 ) at 873 K in high carburizing sodium for 316 steel grades. The apparent diffusion coefficient evaluated from this simple approach was much lower than the diffusion coefficient of carbon extrapolated from high temperature data in austenite [16] validated at lower temperatures [17], D c = 5.6 9 10 -10 cm 2 s -1 at 873 K. This observation was not surprising and was always found for steels containing strong carbide formers, such as chromium.…”

“…This method was used even though this diffusion model does not consider precipitation. This was done in order to compare the results with those obtained in the industry [2,13,14] for basic time of life modelling. D app should be considered only as a fitting parameter which depends strongly on the alloy composition.…”

Investigations of Materials Compatibility Relevant to the Ebr-Ii System.

“…It seems unlikely that the carbon enrichment at the outside surface -was caused by the presence of the carbonaceous flakes. The thickness of the case -was over twice the maximum depth that the data of Agarwala et al 8 would predict for carbon diffusion at this temperature. Further, no case was discernible on the inside surface, even though the carbonaceous flakes were present there.…”

A diffusion driven carburisation combined with a multiaxial continuum creep model to predict random multiple cracking in engineering alloys

“…The extreme case is linear or accelerating rates of empirical laws damage which can occur at extreme temperatures and environments. The second and third can be described by logarithmic and parabolic relationship [6][7][8][9][10][11][12][13] which essentially describe the rate of damage as continually decreasing with time. In some cases the process can deplete or harden the surface and/or can develop a self-healing/protection mechanism, depending on the type of alloy, environment and temperature and oxidation mode which prevents further surface damage.…”

“…Mechanisms such as creep cracking [1][2][3][4][5] and oxidation/carburisation/nitriding [4][5][6][7][8][9][10][11][12][13] have in common a 'rate dependent' damage inducing component. It has been shown that three main categories of damage rate dependencies exist in the oxidation processes.…”