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Dependence of the hydrogen permeation in stainless steel on carbon content, heat treatment and cold work
Author(s) -
Dayal Ravin Kumar,
Grabke Hans Jürgen
Publication year - 2000
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.200001225
Subject(s) - permeation , materials science , annealing (glass) , hydrogen , grain size , metallurgy , grain growth , grain boundary , analytical chemistry (journal) , austenitic stainless steel , dislocation , chemistry , composite material , microstructure , biochemistry , organic chemistry , membrane , corrosion , chromatography
The hydrogen permeation behaviour in austenitic stainless steel (1.4301, AISI 304) was studied between 25 to 85 °C using the electrochemical double cell permeation technique. Influences of parameters like carbon content, grain size and cold work were investigated. Using the current transient plots from the permeation experiments, apparent diffusion coefficient, D app values were calculated. Values ranging from 5.8•10 −12 to 2.7•10 −10 cm 2 /s were obtained for various conditions of the material. The increase in carbon mass content from 0.045 to 0.085 % resulted in a decrease in D app by a factor of 8. This was attributed to the increased blocking of interstitial sites by higher carbon in the latter steel. The annealing treatment, resulting in a slight grain growth caused a decrease in D app to about its half, in contrast to the reduced trapping effect of the grain boundaries. This was explained to be due to a longer hydrogen transport path required through the grain and less contribution of fast diffusion paths in the larger grain size material. A slight cold work (5% reduction in thickness) decreased the D app whereas higher cold working (30 %) increased the D app . The cold working results in an increase in dislocation density and the dislocations act as traps for hydrogen transport. This results in a decrease in D app values for 5 % cold work material. Strain induced martensite (α', bcc phase) formation in the matrix occurred in the higher cold worked material (10 and 30%). The presence of this bcc phase overcame the trapping effect of increased dislocation density resulting in an enhancement of hydrogen transport. From the activation energy calculated, it was concluded that the a' phase present did not provide a continuous medium for hydrogen transport, but added to the overall increase in the hydrogen transport process.