Activity of carbon and solubility of carbides in the FCC Fe-Mo-C, Fe-Cr-C, and Fe-V-C alloys

Wada, Tsuguyasu; Wada, Harue; Elliott, John F.; Chipman, John

doi:10.1007/bf02652854

Cited by 107 publications

(36 citation statements)

References 11 publications

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“…The diffusivity coefficient and the activation energy are constant for the equations from Table 1 However, as illustrated in multiple studies, alloy additions do alter carbon diffusion in austenite. 3,4,6,[15][16][17][18][19] Blanter (as cited in Krishtal 3) ) evaluated the effects of systematic modifications to ternary Fe-M-C alloys. Table 2.…”

Section: Equation For Fe-m-c Alloysmentioning

confidence: 99%

“…12. [15][16][17] and Zhukov and Krishtal 18) investigated the effects of alloying elements on the activity of carbon and the coefficient of carbon diffusivity for ternary Fe-M-C alloys by using thermodynamic calculations correlated with experimental data. Goldstein and Moren 19) studied the influence of cross-diffusion coefficients on carbon diffusion by the additional alloying elements in a simulated carburizing process.…”

Section: Equation For Fe-m-c Alloysmentioning

confidence: 99%

“…Following the work of Wada et al, [15][16][17] who assert that different alloy elements affect carbon activity independently and that the interactions between two alloy elements can be ignored, Eq. (16) (17) where the summation is over the alloying elements present in the steel.…”

Section: Equation For Multicomponent Steel Alloysmentioning

confidence: 99%

“…The same k 1 and k 2 given in Table 4 are used in Eq. (17). Figure 6 compares carbon diffusivities predicted by Eq.…”

Section: Equation For Multicomponent Steel Alloysmentioning

confidence: 99%

“…Such a fundamentally based model has been derived 25) but is computationally more complex, and in many design cases, a sound engineering approach is more than adequate. Equation (17) provides this engineering approach. Figure 7 shows the diffusivities of carbon calculated by two different methods as well as the experimental data.…”

Section: Equation For Multicomponent Steel Alloysmentioning

confidence: 99%

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An Empirical Model for Carbon Diffusion in Austenite Incorporating Alloying Element Effects

2011

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The diffusion of carbon in austenite is important to the design and implementation of many steel heattreating processes. The present study proposes a simple and computationally efficient equation for the diffusion of carbon in austenite for iron-carbon alloys, as well as for steels alloyed with a variety of elements. The proposed empirical model provides a pragmatic engineering approach to this important diffusion process. The model is shown to better match the carbon diffusion profiles of several carburized steel alloys, as compared to other equations that have been reported in the literature. These other equations were primarily obtained from experiments on iron-carbon alloys, and it is not surprising that they are less accurate when compared to the proposed equation that takes the full range of alloy compositions into account.KEY WORDS: carbon diffusion; alloy effects on diffusion in austenite; empirical model; experimental data; steels.

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Section: Equation For Fe-m-c Alloysmentioning

confidence: 99%

Section: Equation For Fe-m-c Alloysmentioning

confidence: 99%

Section: Equation For Multicomponent Steel Alloysmentioning

confidence: 99%

“…The same k 1 and k 2 given in Table 4 are used in Eq. (17). Figure 6 compares carbon diffusivities predicted by Eq.…”

Section: Equation For Multicomponent Steel Alloysmentioning

confidence: 99%

Section: Equation For Multicomponent Steel Alloysmentioning

confidence: 99%

See 3 more Smart Citations

An Empirical Model for Carbon Diffusion in Austenite Incorporating Alloying Element Effects

2011

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Kinetics of the carburization of iron alloys in methane‐hydrogen mixtures and of the decarburization in hydrogen

et al. 1985

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The surface reaction kinetics have been investigated for the reaction CH4 (gas) = C (dissolved) + 2H2 (gas) on Fe and Fe‐M foils (M = Mn, Cr, Co, Ni, Sn) at temperatures between 800 and 1000°C. The resistance relaxation method was applied in a flow apparatus. The following rate equation was observed for the rate of carbon uptake where is the carbon concentration and k and k′ are the rate constants for carburization and decarburization respectively. For Fe, Fe‐10 Ni and Fe‐10 Co the value of v = 3, for the alloys with > 20% Ni as well as for all Fe‐Mn and Fe‐Cr alloys the value v = 4 results from the measurements, which indicates differences in the rate determining step. With increasing Cr, Mn, Ni, Co content the rate constants k and k′ increase. The decrease of the equilibrium carbon concentration with increasing Ni content in Fe‐Ni alloys is correlated to a fast increase of k′ and a slow increase of k with increasing Ni content. Beyond the minimum of at about 70 wt.% Ni both rate constants show a strong increase. By holding Ni at high carbon activities (aC > 0.7 at 1000°C) segregation of carbon induces a surface reconstruction which is characterized by formation of (111) planes and which reduces the reaction rates. The increase of the equilibrium carbon concentration in the systems Fe–Mn and Fe–Cr with increasing content of alloying element is correlated to a slow increase of k′ and a fast increase of k with increasing Mn or Cr content. Sn segregates to the surface and retards the reaction rate by blocking the reaction sites for the surface reaction, similar to the effects of P and S.

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Effect of alloying elements on the microstructure‐property relationship in thermomechanically processed C‐Mn‐Si TRIP steels

Timokhina¹,

Hodgson²,

Pereloma

2002

Steel Research

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The effect of additions of Nb, Al and Mo to Fe‐C‐Mn‐Si TRIP steel on the final microstructure and mechanical properties after simulated thermomechanical processing (TMP) has been studied. The laboratory simulations of discontinuous cooling during TMP were performed using a hot rolling mill. All samples were characterised using optical microscopy and image analysis. The volume fraction of retained austenite was ascertained using a heat tinting technique and X‐ray diffraction measurements. Room temperature mechanical properties were determined by a tensile test. From this a comprehensive understanding of the structural aspect of the bainite transformation in these types of TRIP steels has been developed. The results have shown that the final microstructures of thermomechanically processed TRIP steels comprise ~ 50 % of polygonal ferrite, 7 ‐12 % of retained austenite, non‐carbide bainitic structure and martensite. All steels exhibited a good combination of ultimate tensile strength and total elongation. The microstructure‐property examination revealed the relationship between the composition of TRIP steels and their mechanical properties. It has been shown that the addition of Mo to the C‐Si‐Mn‐Nb TRIP steel increases the ultimate tensile strength up to 1020 MPa. The stability of the retained austenite of the Nb‐Mo steel was degraded, which led to a decrease in the elongation (24 %). The results have demonstrated that the addition of Al to C‐Si‐Mn‐Nb steel leads to a good combination of strength (~ 940 MPa) and elongation (~ 30 %) due to the formation of refined acicular ferrite and granular bainite structure with ~7 ‐ 8 % of stable retained austenite. Furthermore, it has been found that the addition of Al increases the volume fraction of bainitic ferrite laths. The investigations have shown an interesting result that, in the Nb‐Mo‐Al steel, Al has a more pronounced effect on the microstructure in comparison with Mo. It has been found that the bainitic structure of the Nb‐Mo‐Al steel appears to be more granular than in the Nb‐Mo steel. Moreover, the volume fraction of the retained austenite increased (12 %) with decreasing bainitic ferrite content. The results have demonstrated that this steel has the best mechanical properties (1100 MPa and 28 % elongation). It has been concluded that the combined effect of Nb, Mo, and Al addition on the dispersion of the bainite, martensite and retained austenite in the ferrite matrix and the morphology of these phases is different than effect of Nb, Mo and Al, separately.

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Activity of carbon and solubility of carbides in the FCC Fe-Mo-C, Fe-Cr-C, and Fe-V-C alloys

Cited by 107 publications

References 11 publications

An Empirical Model for Carbon Diffusion in Austenite Incorporating Alloying Element Effects

An Empirical Model for Carbon Diffusion in Austenite Incorporating Alloying Element Effects

Kinetics of the carburization of iron alloys in methane‐hydrogen mixtures and of the decarburization in hydrogen

Effect of alloying elements on the microstructure‐property relationship in thermomechanically processed C‐Mn‐Si TRIP steels

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