Kinetics of carburizing in an endothermal atmosphere

Moiseev, B. A.; Brunzel, Yu. M.; Shvartsman, L. A.

doi:10.1007/bf00780479

Cited by 11 publications

(8 citation statements)

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“…In this case, the assumption of constant surface carbon content can be justified. In practice, however, the carbon transfer from the atmosphere to the steel surface is often reported to be the rate-limiting factor, [4,5] especially at the start of the carburizing process. After this initial stage, the process becomes mixed controlled, [8][9][10][11] and should be modeled correspondingly.…”

Section: Kinetics Of Carbon Transfer In Carburizingmentioning

confidence: 99%

“…More accurate modeling of the gascarburizing process must account for mass transfer from the carburizing gas atmosphere to the steel surface, the surface reaction, and further carbon diffusion into the steel. Mass transfer in the gas atmosphere is the rate-limiting factor in the initial stages of carburizing, [4,5] and carbon diffusion controls the process at longer times [6,7] ; more often, however, carburizing is considered to be controlled by a combination of both factors. [8][9][10][11] If these coefficients could be calculated from the This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A.…”

Section: Introductionmentioning

confidence: 99%

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Carbon Diffusion in Steels: A Numerical Analysis Based on Direct Integration of the Flux

Karabelchtchikova¹,

Sisson²

2006

Journal of Phase Equilibria & Diffusion

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In the early 1970s, Professor Dayananda developed a technique for the direct integration of fluxes from the concentration profiles in vapor-solid diffusion couples to determine diffusion coefficients and atomic mobilities. As part of a project to control and optimize the industrial carburization process in mild-and low-alloyed steels, a modified integration analysis was applied to determine the mass transfer coefficient in the gas boundary layer and carbon diffusivity in austenite. Because carbon flux and surface carbon content vary with time during single-stage carburizing even with a fixed carbon potential in the atmosphere, a mass balance at the gas-solid interface must serve as a boundary condition. This article discusses the numerical modeling of gas carburizing, and focuses on calculating the mass transfer and carbon diffusivity parameters using the simulated concentration profiles. This approach validates the proposed method by comparing the calculated parameters with those used in simulation. The results were compared with previous determinations and predictions reported in the literature.

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Section: Kinetics Of Carbon Transfer In Carburizingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Carbon Diffusion in Steels: A Numerical Analysis Based on Direct Integration of the Flux

Karabelchtchikova¹,

Sisson²

2006

Journal of Phase Equilibria & Diffusion

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“…The thermal equilibrium parameters can be monitored and controlled by the maturely developed probes for O 2 , H 2 O, and CO 2 , and thermal couples, while the kinetic parameters should be designed based on the properties of the steels and the interactions on the steel/gas interface. By linear non-equilibrium thermodynamics, the kinetics of carburizing is governing by the so-called duration of carbon potential build-up (τ CP , s), the surface transfer coefficient of carbon (β, cm•s −1 ), and the bulk diffusion coefficient of carbon (D, cm 2 •s −1 ). It is usually pre-assumed that the build-up of carbon potential is relatively fast by rational design of convective flow of gases, Coatings 2022, 12, 1886 2 of 14 while the surface transfer and bulk diffusion of carbon are considered as the rate-limiting steps [2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…By linear non-equilibrium thermodynamics, the kinetics of carburizing is governing by the so-called duration of carbon potential build-up (τ CP , s), the surface transfer coefficient of carbon (β, cm•s −1 ), and the bulk diffusion coefficient of carbon (D, cm 2 •s −1 ). It is usually pre-assumed that the build-up of carbon potential is relatively fast by rational design of convective flow of gases, Coatings 2022, 12, 1886 2 of 14 while the surface transfer and bulk diffusion of carbon are considered as the rate-limiting steps [2][3][4][5][6]. Therefore, β and D are vital to the rational design of carburizing process of specific steels.…”

Section: Introductionmentioning

confidence: 99%

Measurements of Carbon Diffusivity and Surface Transfer Coefficient by Electrical Conductivity Relaxation during Carburization: Experimental Design by Theoretical Analysis

Sheng²,

Wang

et al. 2022

Coatings

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The diffusion coefficient (D) and surface transfer coefficient (β) of carbon are important parameters governing the kinetics of carburization, and some other heat treatment processes accompanied by redistribution of carbon in steel. Here, we propose to use an electrical conductivity relaxation (ECR) method for the in situ measurement of D and β of carbon. The feasibility of the method is discussed by the theoretical modeling of carburization for an infinitely long rectangular sample. The synthetic ECR data for the carburization is simulated by tracking the relaxation of electrical conductivity upon a sharp or a gradual change of carbon potential. Then, by Fourier transform, the synthetic ECR data is transformed to an impedance spectroscopy, which is used for estimation of D and β by fitting with a one-dimensional equivalent circuit model. The effects of the width-to-thickness ratio of the sample and the duration of carbon potential buildup on the accuracy of the estimated D and β are studied. The feasibility of the ECR method is verified, and rational guidance for experimental design is proposed.

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“…The process occurs due to the carbon diffusion in the steel and is used to enhance mechanical and chemical properties of steel components in mechanical, automotive and aerospace devices. The quality of the carburized parts depends on the carbon distribution (case depth and concentration) [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%