Hydrogen transport and embrittlement for palladium coated vanadium—chromium—titanium alloys

Abstract

As part of a study of the thermodynamics, kinetics and embrittlement properties of hydrogen in vanadium based alloys, experiments were conducted to determine the rate of hydrogen transport through the vanadium reference alloys, V-7.5Cr-15Ti and V-4Cr-4Ti, and to determine these alloys' hydrogen embrittlement, they were exposed to hydrogen pressures of 3 and 300 kPa (0.03-3 atm) at temperatures between 380 and 475°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 pmoles/(m2sPao*5) for the V-7.5Cr-15Ti alloy and 0.02 to 0.05 pmoles/m2sPaO.5 for the V-4Cr-4Ti alloy depending on the quality of the coat and the operating temperature. At 1.7 am hydrogen, V-7.5Cr-lSTi embrittled at temperatures below 380' C while V-4Cr4Ti embrittled around 330O C

Influence of heat treatment on hydrogen ingress into V–4Cr–4Ti alloy

“…Hence, the permeation rates for V-4Cr-4Ti alloy membranes under the surface conditions of Specimens AP and HT were evaluated from the presently obtained values of a by assuming surface-limited permeation, and they were compared with the permeation rates calculated from the data on permeability given by Shkolnik et al [12]. The permeability data reported by other researchers for Pdcoated V-4Cr-4Ti [13] and V-6Cr-5Ti [7] alloys were also subjected to similar comparison. In the surfacelimited regime, the permeation rate / P is expressed as / P ¼ aP 1 A= ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 8pmRT p , provided that the properties of upstream and downstream surfaces are identical, i.e.…”

“…The permeation rate of hydrogen through a V-4Cr-4Ti alloy membrane in the surface-limited regime was evaluated from the values obtained for the absorption coefficient to compare with the data reported by Shkolnik et al [12] and other researchers [7,13], and the influence of surface composition on the hydrogen permeation was discussed.…”

Alloying effects on hydrogen permeability of V without catalytic Pd overlayer

“…Therefore, for such non Pd-based alloy membranes, the catalytic Pd overlayers on the surface are considered to be essential to obtain practical hydrogen flux through them [9]. However, another problem arises when such Pd-coated composite membranes are used at high temperature, i.e., a significant degradation of hydrogen permeability occurs within a short time due to the interdiffusion of base metal and palladium to form intermetallic compounds such as Pd 3 Nb [10].…”

Effects of simultaneous transfer of heat and tritium through Li–Pb or Flibe blanket

“…Sh = de breeder /l breeder are assumed. *2) Since the pressure dependence of permeation is different from the square-root rule[10] (S SiC-H D SiC-H ) value at pT 2 = 1 × 10 5 Pa is used for the calculation of BiT.…”