Foundamental Researches on the Behavior of Hydrogen in Steels (Part 3)

Effect of Microstructure on Permeability of Hydrogen in Steels

Abstract

In the previous papers, the diffusivity of hydrogen in steel could be explained comparatively well by using the Fick's second law, assuming that steel was homogeneous on the whole.
In this report, using the steel specimens varied in structures, the effects of the structures on the diffusion coefficient of hydrogen were described.
The experimental data which were obtained from the permeability tests were analyzed by using the Time Lag method, and from its analysis, the diffusion coefficients of hydrogen in some structures of steel were calculated.
The results obtained are as follows;
(1) The hydrogen diffusivity depends upon the structure of steel. The ferrite+pearlitc structure has a large diffusivity, and the martensite has a small one. This tendency of the hydrogen diffusivity well agrees with the results from the hydrogen occlusion test.
(2) The solubility of hydrogen in each structure is respectively 40cc/100gFe (ferrite+pearlite), 26cc/100gFe(troostite) and 24cc/100gFe (martensite). These values are consistent with the results from the hydrogen occlusion test.