CO-N₂雰囲気における鉄の浸炭

抄録

Carburization of iron foils of different thicknesses has been studied under CO-N₂ atmosphere at 1173-1203 K by using an automatic microbalance. The rate of carburization was constant at the initial stage and then gradually decelerated by diffusion of carbon in the iron specimen until it was saturated with carbon. The initial rate was independent of the specimen thickness and probably controlled by a surface reaction. It was proportional to the partial pressure of CO at high pressures and to the square of the partial pressure at low pressures. This behavior was well explained by a kinetic equation that was derived by assuming a rate-controlling desorption of adsorbed oxygen atom created by dissociation of CO. The kinetic parameters of the surface reaction were obtained on the basis of the kinetic equation. The retardation of carburization reaction by diffusion in iron was discussed on the basis of a kinetic equation that was derived by solving the Fick’s equation in the presence of surface reaction. Discussion was made especially on the effects of the specimen thickness, the kinetic parameters of surface reaction and the diffusion constant on the rate of carburization.