HYDROGEN TRANSPORT AND EMBRITTLEMENT FOR PALLADIUM COATED VANADIUM-CHROMIUM-TITANIUM ALLOYS

As part of a study of the thermodynamics, kinetics and embrittlement p roperties of hydrogen in vanadium based alloys, experiments were condu cted to determine the rate of hydrogen transport through the vanadium reference alloys, V-7.5Cr-15Ti and V-4Cr-4Ti, and to determine these a lloys' hydrogen embrittlement, they were exposed to hydrogen pressures of 3 and 300 kPa (0.03-3 atm) at temperatures between 380 and 475 deg rees C. To facilitate hydrogen entry and egress, tubes of these alloys were coated with palladium on the inside and outside faces. Observed permeabilities were 0.015 to 0.065 mu mol/(m(2) s Pa-0.5) for the V-7. 5Cr-15Ti alloy and 0.02 to 0.05 mu mol/(m(2) s Pa-0.5) for the V-4Cr-4 Ti alloy depending on the quality of the coat and the operating temper ature. At 1.7 atm hydrogen, V-7.5Cr-15Ti embrittled at temperatures be low 380 degrees C while V-4Cr-4Ti embrittled around 330 degrees C.