Published: Jan 1988
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The influence of strain and strain rate on hydrogen entry, transport, and trapping in high-strength ferrous alloys and the subsequent effects on hydrogen embrittlement are being investigated in this research program. Most hydrogen permeation measurements reported in the literature presume surface absorption kinetics to be sufficiently fast as to not influence observed changes in the permeation flux. It is interesting that hydrogen recombination poisons (enhancing absorption) are frequently used to observe permeation currents. It is also interesting that environmental slow-strain-rate plastic loading and cyclic loading at low frequency, possibly enhancing either absorption or bulk diffusion of hydrogen, have been observed to increase tendencies towards hydrogen embrittlement. In the present investigation a series of slow-strain-rate measurements, electrochemical measurements to investigate adsorption-absorption kinetics and eventually a combination of these, are being performed and will be described. A discussion of electrochemical techniques being utilized for adsorption-absorption studies is included. It is anticipated that once this program is completed, the influence of plastic deformation on the hydrogen absorption and apparent hydrogen diffusion rate for a high-strength steel will be assessed. Once the effects of surface absorption and bulk diffusion are differentiated, the influence of each will be correlated with the degree of hydrogen-stimulated environmental damage observed for AISI 4340 steel in chloride environments.
hydrogen, hydrogen embrittlement, adsorption, absorption, surface coverage, strain rate, diffusion, plasticity, permeability, film rupture, hydrogen trapping, solubility, concentration
Scully, John R.
Sandia National Laboratories, Albuquerque, NM
Moran, Patrick J.
Associate professor, Department of Materials Science, The Johns Hopkins University, Baltimore, MD