On the Phase-Change in Gas Carbo-Nitriding Process

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  • ガス浸炭窒化処理過程における相変化について
  • ガス シンタン チッカ ショリ カテイ ニ オケル ソウヘンカ ニ ツイテ

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Abstract

Steel foil samples were used as before, in order to get a uniform structure in a short time treatment, and to make it clear what kind of phase the surface layer would pass through, at carbo-nitriding, in the process of reaching the equilibrium value. Taking it for granted that when the electric-resistance change was measured and it was observed that change in phase took place, there would be a sudden change in electric resistance. The following results were obtained:—(1) At 850∼600°C, when carbo-nitrization began a sudden rise in electric resistance occured, making the saturation curve reached the equilibrium value. (2) Another sample, that was treated under the same condition as in (1), was taken out at times, was analyzed by X-ray, and it was proved that the sudden change in electric resistance was caused by a change in phase. (3) At 850∼650°C the carburizing got through the process of α-γ-ε and balanced at ε-phase. (4) At 600°C, the process of α-γ′-ε is gone through and without passing the γ-area,carbo-nitriding goes on. This γ′-phase corresponds to γ′-phase of Fe-N system and is different from γ-phase of (3). The lattice constant (a) is 3.783Å. Therefore it became clear that the treatment proved to be below the ternary transformation.

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