Enhanced Carbon Diffusion in Austenitic Stainless Steel Carburized at Low Temperature

Ernst, F.; Avishai, Amir; Kahn, H.; Gu, Xin; Michal, G. M.; Heuer, A. H.

doi:10.1007/s11661-009-9854-9

Cited by 53 publications

(39 citation statements)

References 30 publications

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“…The slightly convex shape of the concentration profile is due to the strong concentration dependence of the diffusion coefficient of carbon in austenite, D C (X C ). [10] The~20-lm-thick case depth revealed by this analysis is consistent with the optical metallographic and MFM analyses. Finally, the corresponding hardness profile is also shown.…”

Section: Resultssupporting

confidence: 83%

Paraequilibrium Carburization of Duplex and Ferritic Stainless Steels

Michal

Jennings

Kahn

et al. 2009

Metall Mater Trans A

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AISI 301 and E-BRITE stainless steels were subjected to low-temperature (743 K) carburization experiments using a commercial technology developed for carburization of 316 austenitic stainless steels. The AISI 301 steel contained~40 vol pct ferrite before carburization but had a fully austenitic hardened case,~20-lm thick, and a surface carbon concentration of~8 at. pct after treatment; this ''colossal'' paraequilibrium carbon supersaturation caused an increase in lattice parameter of~3 pct. The E-BRITE also developed a hardened case, 12-to 18-lm thick, but underwent a more modest (~0.3 pct) increase in lattice parameter; the surface carbon concentration was~10 at. pct. While the hardened case on the AISI 301 stainless steel appeared to be single-phase austenite, evidence for carbide formation was apparent in X-ray diffractometer (XRD) scans of the E-BRITE. Paraequilibrium phase diagrams were calculated for both AISI 301 and E-BRITE stainless steels using a CALPHAD compound energy-based interstitial solid solution model. In the low-temperature regime of interest, and based upon measured paraequilibrium carbon solubilities, more negative Cr-carbon interaction parameters for austenite than those in the current CALPHAD data base may be appropriate. A sensitivity analysis involving Cr-carbon interaction parameters for ferrite found a strong dependence of carbon solubility on relatively small changes in the magnitude of these parameters.

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Section: Resultssupporting

confidence: 83%

Paraequilibrium Carburization of Duplex and Ferritic Stainless Steels

Michal

Jennings

Kahn

et al. 2009

Metall Mater Trans A

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“…The plots further confirm the above conclusions as to which model profiles are most appropriate for the description of the diffusion coefficient. This can also be deduced from the root mean square errors between our analytical results and the numerical results from [39] and [40] (see Table 6). …”

Section: Resultsmentioning

confidence: 61%

“…One example is the carbon diffusion in an austenitic stainless steel investigated in [39], where the carbon fraction was measured in dependence on the depth below the steel surface to which the carbon extended after carburization (see Fig. 1(a)).…”

Section: Resultsmentioning

confidence: 99%

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Model formulas for facilitating determination of concentration-dependent diffusion coefficients

Medved

Černý

2015

Met. Mater. Int.

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Several formulas for determining the concentration dependence of diffusion coefficients are introduced for a one-dimensional semi-infinite diffusion problem, applying the Boltzmann-Matano method to "S-shaped" concentration profiles approximated by model functions. The functions are expressed in terms of the Gauss error function, hyperbolic tangent, exponential, and inverse tangent. For all model profiles the corresponding formulas for the diffusion coefficient are calculated. Rapid estimates of the diffusion coefficient are also provided as simple expressions obtained by evaluating the formulas at the center of the concentration profile. The results for the individual profiles are compared, and it is demonstrated that even very similar profiles can lead to rather different diffusion coefficients, especially at low concentrations. Using two examples of different diffusion processes, it is demonstrated that the results can be employed to rapidly calculate diffusion coefficients. In addition, it is shown that a finite diffusion coefficient at low concentrations only occurs if the corresponding concentration profile decays at a Gaussian rate or faster.

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“…As discussed in the previous paper, 11) carbide precipitation around the layered-steel interfaces is driven by a steep change of C chemical potential across the interface; i.e. C diffusion is sufficiently fast even at the present annealing temperature of 500°C (diffusion coefficient of C in an AISI316 austenitic stainless steel, whose composition is similar to that of the AISI304, is 10 -16 m 2 /s at 453°C 16) ). We find that the thin oxide layer (Fig.…”

Section: Resultsmentioning

confidence: 81%

Complex Oxide Layer at a Nickel/Steel Interface Bonded under a Moderate Vacuum Condition

2011

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Microstructures of a nickel/austenitic-steel (AISI304) interface, which has been bonded through in-situ cold-rolling of clean surfaces (pre-sputtered by argon ion) within a vacuum apparatus (~10 -3 Pa), then followed by an annealing at 500°C, are investigated by transmission electron microscopy. We frequently find significant traces of thin oxide layers of 5-10 nm in thickness, which commonly reveal complex microstructures composed of bi-layers of different types of oxides. Origin of such interface oxides is presumably due to a slight oxygen contamination of the sputtered-surface in the present moderate vacuum condition, and the oxide precipitation at the bonded-interface has been promoted during annealing. Concerning that the strength of the present Ni/steel cold-rolled interface remarkably increases during an early stage of the annealing at 500°C, it is concluded that their strong interface bonding is supported both by nanometeric oxide-layers as well as direct metal/metal contacts. KEY WORDS: interface structure; surface activated bonding (SAB); scanning transmission electron microscopy; diffusion bonding.

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Enhanced Carbon Diffusion in Austenitic Stainless Steel Carburized at Low Temperature

Cited by 53 publications

References 30 publications

Paraequilibrium Carburization of Duplex and Ferritic Stainless Steels

Paraequilibrium Carburization of Duplex and Ferritic Stainless Steels

Model formulas for facilitating determination of concentration-dependent diffusion coefficients

Complex Oxide Layer at a Nickel/Steel Interface Bonded under a Moderate Vacuum Condition

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