Hydrogen diffusivity in Fe40Ni38Mo4B18 amorphous metallic alloys

Samples of amorphous Fe40Ni38Mo4B18 alloy were submitted to electrochemical hydrogen permeation tests, under cathodic charging conditions, which resulted in high hydrogen fugacity. It was observed that the apparent hydrogen diffusivity is dependent on the hydrogen concentration applied. For cathodic charging levels of -1.15 and -1.35 V/SCE (SCE, Standard Calomel Electrode), the hydrogen permeation curves exhibit a single sigmoidal shape, typical of the tests where no hydride formation occurs. For higher applied cathodic potentials (-1.65, -1.80 and -2.00 V/SCE), strong deviations were observed from the theoretical curve shape which suggests the formation of a hydride phase across the thickness of the alloy. The value of the hydrogen apparent diffusion coefficient in the beta-phase hydride formed in the amorphous Fe40Ni38Mo4B18 alloy was found to be equal to 6.0x10(-15) m(2) s(-1) at an applied cathodic potential of -2.00 V/ SCE, at 40 degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.