Hydrogen permeability and erosion behavior of W–Pd bimetallic systems

The erosion behavior of W–Pd bimetallic systems has been investigated for both hydrogen-saturated (H/Pd ∼ 0.65) and unsaturated states during impact of a steady-state nitrogen plasma from a mirror Penning discharge. An essential decrease by factors of about 2–5 in the erosion rate of W was observed for hydrogen-saturated W–Pd samples in the nitrogen ion energy range from 0.8 to 1.6 keV. Possible reasons for this erosion behavior are discussed. Isotherms and isobars of hydrogen permeability through W–Pd systems were measured in the temperature range of 573–973 K and hydrogen pressure range of 1.33 × 102 to 105 Pa. It is shown that the limiting stage of permeation process is, most likely, the diffusion in the W film. The activation energy of hydrogen permeability was determined to be ∼12 kJ/mol, this being much lower than the literature data for bulk tungsten at molecular hydrogen-driven permeation. Possible mechanisms are suggested and analyzed to explain the observed decrease in the activation energy of hydrogen penetration through W–Pd systems.