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Vol.17, No.6, 455 ~ 468, 1979

Title

Studies on the Growth of γ' - phase ( Fe4N ) in the Iron - Nitrogen System

장충근Choong Kun Chang, 이재영Jai Young Lee, 김수영Soo Young Kim

Abstract

The growth kinetics of the intermediate nitride, the γ´-phase (Fe₄N), in the iron-nitrogen binary system was observed by assuming the diffusion control in multiphase diffusion. The observed growth rate of the γ´-phase was given by dX_(III)/dt=(M/ρ)Fe₄N·5/4·D_(III)ΔC_(III)/X_(III) (1) and the depth of the γ´-phase layer by X_(III)=[10/4(M/ρ)Fe₄N·D_(III)ΔC_(III)]^½·t½ (2) On the other hand, the diffusion coefficient of nitrogen obtained from the quantity of nitrogen diffused into the cylindrical sample of pure iron and the saturation value of the nitrogen in the temperature range of 650℃-900℃ was given by D=1.3×10^(-2)exp[-28300/RT]㎠/sec (3) The diffusion coefficient obtained by substituting the depth of γ´-phase generated in the sample in to Eq. (2) was D=2.9×10^(-2)exp[-27700/RT]㎠/sec (4) from which we may notice a good agreement with Eq. (3). However, the result obtained by treating the diffusion of nitrogen in a single phase was D=1.6×10^(-4)exp[-18600/RT]㎠/sec (5) showing discrepancy with the above results.

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