Nitrogen diffusion through cementite layers

Nikolussi, Marc; Leineweber, Andreas; Mittemeijer, E. J.

doi:10.1080/14786430903292365

Cited by 23 publications

(13 citation statements)

References 28 publications

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“…[91] At lower temperatures, h layers can be produced on Fe substrates by heat treatment in an atmosphere containing CO, NH 3 , and H 2 . [92] During the treatment, the substrate is gradually saturated with N that has diffused through h, [93] eventually leading to formation of an e layer underneath the h layer. [50] h produced under these conditions has been investigated by atom probe tomography, [94] revealing, nevertheless, a maximum total impurity content of only 0.01 at.…”

Section: B Ternary Fe-n-c Datamentioning

confidence: 99%

Thermodynamics of the Fe-N and Fe-N-C Systems: The Fe-N and Fe-N-C Phase Diagrams Revisited

Göhring

Fabrichnaya

Leineweber

et al. 2016

Metall Mater Trans A

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Several thermodynamic descriptions of the Fe-N and Fe-N-C systems were proposed before now. The results of these descriptions significantly deviate from more recently obtained experimental data. The present work provides a revised thermodynamic description of these systems. The new description for the Fe-N system agrees distinctly better with the experimental data especially for the equilibrium of c 0 -Fe 4 N 1Àx and e-Fe 3 N 1+z . The new thermodynamic description for the Fe-N-C system considering the Fe-rich part of the system with less than 33 at. pct N and less than 25 at. pct C excellently agrees with the new experimental data for both the temperatures of the invariant reactions and the phase boundaries. This in particular concerns the temperature range of typical technical nitriding and nitrocarburizing treatments [723 K to 923 K, (450°C to 650°C)], within which three invariant reactions occur in the ternary system.

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Section: B Ternary Fe-n-c Datamentioning

confidence: 99%

Thermodynamics of the Fe-N and Fe-N-C Systems: The Fe-N and Fe-N-C Phase Diagrams Revisited

Göhring

Fabrichnaya

Leineweber

et al. 2016

Metall Mater Trans A

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“…These substrates exposet he difficultyo fe stablishing certain solid-state equilibria uponn itrocarburising Nfree (pure) a -ironsubstrates [40]due to initial formation of cementite layers actinga sadiffusion barrier for nitrogen [41]. c. So-called secondary anneals under inert atmosphere applied to specimensp reviously nitrocarburised at temperatures identicalt oo rd ifferent from the annealing temperature [38,39,42].…”

Section: Introductionmentioning

confidence: 99%

Fe–N and Fe–N–C phase equilibria above 853 K studied by nitriding/nitrocarburising and secondary annealing

Woehrle

Cinaroglu

Leineweber

et al. 2016

International Journal of Materials Research

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Compound-layer microstructures obtained by gaseous nitriding and nitrocarburising treatments of α-Fe and Fe–N alloy and by subsequent treatments were analysed to obtain new information on the metastable Fe–N and Fe–N–C systems above 853 K at 1 atm. In the case of the binary Fe–N system, invariant temperatures and phase boundaries agree well with the literature data, only the γ/γ + γ' and the γ/γ + ∊ boundaries as determined in the present work by means of electron probe microanalysis are located at N contents up to 1 at.% lower than reported in previous works. In the case of the ternary Fe–N–C system, the invariant eutectoid reaction was found to occur in the range 853 K – 863 K, whereas the invariant transition reaction was found to occur in the range 868 K – 873 K. The obtained data were used to draw isothermal sections of the Fe–N–C system for 853 K and 893 K. The determined temperatures for the invariant eutectoid and transition reactions as well as the extent of the ternary ∊-phase field were compared with phase diagrams calculated on the basis of different thermodynamic descriptions of the Fe–N–C system.

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“…The second study has reported the nitrogen diffusion process in the bcc Fe plate with Fe 3 C coat layers. 20) In this case, nitrogen atoms passed through the Fe 3 C layers and reached the inner bcc-Fe during the diffusion and then both diffusion constants for nitrogen in the Fe 3 C and bcc-Fe layers were determined. The diffusion constant in the Fe 3 C layer is three orders of magnitude smaller than that in bcc Fe.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of ε-FexN (2≤x≤3) Submicron Particles and the Diffusion Mechanism of Nitrogen Atoms

et al. 2010

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We synthesized submicron-sized "-Fe x N (2 5 x 5 3) particles by heating 180-nm Fe 3 O 4 particles in an atmosphere of NH 3 , both with and without H 2 , and we studied their structural and magnetic properties. The nitride samples (first step nitridation) prepared by NH 3 and annealed at 623 K ("-Fe 2 N) had an expanded unit cell and were paramagnetic at room temperature. The purpose of H 2 annealing, which was successively applied on the first step nitride sample, was to dissolve excess nitrogen atoms and reduce the lattice constant. The nitrogen concentrations were estimated from X-ray diffraction patterns. Saturation magnetization was found to increase with the H 2 annealing time. The nitrogen diffusion constant in the submicron hcp particles was found to be 6:33 Â 10 À20 m 2 /s, which is about three orders of magnitude smaller than that of the bulk hcp iron nitrides. This may result from the coating materials, such as SiO 2 and others, covering the inner core nitrides, where nitrogen atoms passed through during diffusion.

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Nitrogen diffusion through cementite layers

Cited by 23 publications

References 28 publications

Thermodynamics of the Fe-N and Fe-N-C Systems: The Fe-N and Fe-N-C Phase Diagrams Revisited

Thermodynamics of the Fe-N and Fe-N-C Systems: The Fe-N and Fe-N-C Phase Diagrams Revisited

Fe–N and Fe–N–C phase equilibria above 853 K studied by nitriding/nitrocarburising and secondary annealing

Synthesis of ε-Fe<I><SUB>x</SUB></I>N (2≤<I>x</I>≤3) Submicron Particles and the Diffusion Mechanism of Nitrogen Atoms

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Nitrogen diffusion through cementite layers

Cited by 23 publications

References 28 publications

Thermodynamics of the Fe-N and Fe-N-C Systems: The Fe-N and Fe-N-C Phase Diagrams Revisited

Thermodynamics of the Fe-N and Fe-N-C Systems: The Fe-N and Fe-N-C Phase Diagrams Revisited

Fe–N and Fe–N–C phase equilibria above 853 K studied by nitriding/nitrocarburising and secondary annealing

Synthesis of &epsilon;-Fe<I><SUB>x</SUB></I>N (2&le;<I>x</I>&le;3) Submicron Particles and the Diffusion Mechanism of Nitrogen Atoms

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Synthesis of ε-Fe<I><SUB>x</SUB></I>N (2≤<I>x</I>≤3) Submicron Particles and the Diffusion Mechanism of Nitrogen Atoms