DIFFUSION-COEFFICIENTS OF HYDROGEN IN CARBON-STEELS BETWEEN 278-K AND 318-K AND HYDROGEN TRAPPING EFFECT OF INTERFACE BETWEEN CEMENTITE AND FERRITE

Diffusion coefficients of hydrogen in 0-0.6 mass% carbon steels with spheroidized cementite-ferrite and pearlite-ferrite structures have been measured by the electrochemical permeation method at 278-318 K. The temperature and carbon concentration dependence of the diffusion coefficients has been discussed by using a simple trapping model. The diffusivity of hydrogen is lowered with increasing carbon concentration and depends on the specimen structure. This is caused by the trapping effects of cementite-ferrite interfaces and dislocations. The binding energy between the cementite-ferrite interface and a hydrogen atom is slightly less for the planar cementite than that for the spherical cementite.