Hydrogen permeation characteristics of multi-phase Ni-Ti-Nb alloys

Hydrogen permeation characteristics of ternary Ni-Ti-Nb alloys were investigated using a mass flow meter in the pressure range of 0.2-0.97 MPa on the upstream side and the temperature range of 523-673 K. Hydrogen permeation through the as-cast alloys with Ti and Ni of 20 mol% and less could not be measured by brittleness and by hydrogen brittleness, respectively. Hydrogen permeability of the ductile B2-NiTi phase was 10(-10) mol H, (m(-1) s(-1) Pa-0.5), and increased when alloying with Nb. The Ni30Ti31Nb39 alloy provided a hydrogen permeability of 1.93 x 10(-8) mol H, (m(-1) s(-1) Pa-0.5) at 673 K, which was equivalent to that of pure Pd measured under the same conditions. The Ni30Ti31Nb39 alloy consisted of the primary phase, bcc-NbTi, and the eutectic phases, NiTi + NbTi. The eutectic phases played a major role in prevention of hydrogen brittleness of the NbTi phase, while the NbTi phase contributed mainly to the hydrogen permeation of this duplex alloy. This paper represents the observation of hydrogen permeation in the multiphase alloys for the first time. (C) 2003 Elsevier B.V. All rights reserved.