Diffusion during chemicothermal treatment of carbon alloys

Kvishtal, M. A.; Mokrov, A. P.; Zakharov, Pavel N.

doi:10.1007/bf00651743

Cited by 2 publications

(3 citation statements)

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“…For carbon concentration profiles with less than 1 wt.% C, the mass-transfer coefficient is often expressed as the ratio between the rate coefficient for the chemical reactions and the carbon activity at the steel surface. [17,18] b ¼ X n i k i a surf i ! The mass-transfer coefficient (b) has been reported to be a complex function of the atmosphere gas composition, carburizing potential, and temperature.…”

Section: Introductionmentioning

confidence: 99%

Effect of Alloy Composition on Carburizing Performance of Steel

Rowan

Sisson

2009

J. Phase Equilib. Diffus.

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This paper investigates the effect of alloy composition on the gas carburizing performance of AISI 1018, 4820, 5120, and 8620 steels. The mass-transfer coefficients and carbon diffusivities were calculated from experimental measurements using direct flux integration. Although steels with high concentration of austenite-stabilizing elements (Si, Ni) increased carbon diffusivity in austenite, they significantly reduced the kinetics of carbon transfer from the atmosphere to the steel surface and resulted in lower weight gain. Despite lowering the carbon diffusivities, steels alloyed with carbide-forming elements (Cr, Mo) significantly increased the mass-transfer coefficient in the atmosphere and enhanced the rate of carbon profile evolution. The experimentally determined carbon diffusivities were in good agreement with the carbon diffusivities obtained from the thermodynamic and kinetic databases in DICTRA. Overall, using the concentration dependent mass-transfer coefficient and carbon diffusivity in various alloy steels helped explain the experimentally observed variations in the carbon concentration profiles and the effective case depths. Recommendations are made to help achieve better case depth uniformity within a carburizing workload.

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Section: Introductionmentioning

confidence: 99%

Effect of Alloy Composition on Carburizing Performance of Steel

Rowan

Sisson

2009

J. Phase Equilib. Diffus.

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“…In order to solve the problem, Ram-Mohan and Dayananda [19,20] have proposed a new technique called the transfer matrix method (TMM) for obtaining error function solutions for a diffusion couple with any number of components and have illustrated its use for quaternary Cu-Ni-Zn-Mn diffusion couples [21]. At the same time, when many attempts were made to devise methods to evaluate the diffusion coefficients of multicomponent systems [22][23][24][25][26], Dayananda et al [27,28] have proposed an approach to solving the problem and defining a parameter, the average effective interdiffusion coefficient, which represents the diffusion coefficient averaged over a selected range of compositions for a particular component. Such a parameter can satisfactorily explain the diffusion behavior in many multicomponent systems, such as Fe-Ni-Cr-X (X = Si, Ge) [29], 17-4 PH steel-Ni [30], and L1 2 -Ni 3 Al with ternary alloying addition of Re [31].…”

Section: Introductionmentioning

confidence: 99%

“…This parameter, however, cannot be used for describing all elements of the diffusivity matrix, [D], in systems more complicated than the ternary system. Therefore, square root diffusivity analysis has been used to measure the diffusivity matrix, [D], of systems with more complicated ternary system if the composition-dependence diffusivities are neglected [23]. This assumption is usually valid when the concentration differences across a diffusion couple approach zero [32].…”

Section: Introductionmentioning

confidence: 99%