Effects of W on hydrogen transport property of Nb45Ti27.5Ni27.5 alloy membranes

Alloying influences of tungsten (W) into Nb45Ti27.5Ni27.5 on the microstructure, hydrogen solubility, diffusivity, permeability and resistance to hydrogen embrittlement have been investigated. Four experimental temperatures (673, 623, 573 and 523 K) have been used. It is found that the addition of W (5 at.% and 10 at.%) reduces the hydrogen solubility. The constitution of phases is not changed with W addition, whereas volume fraction of primary bcc-niobium (Nb) phase is distinctly reduced for the content of 10 at.% W. The hydrogen permeability and diffusivity increase for Nb40W5Ti27.5Ni27.5 only at lower temperatures such as 573 K and 523 K. Addition of 10 at.% W causes an obvious reduction in the permeability and diffusivity. The Nb45Ti27.5Ni27.5 alloy membrane fractures at 125∘C, while Nb40W5Ti27.5Ni27.5 and Nb35W10Ti27.5Ni27.5 alloy membranes keep intact when temperature reaches to 100∘C. In comparison with Nb45Ti27.5Ni27.5, the present research confirms that Nb40W5Ti27.5Ni27.5 exhibits an enhancement in hydrogen permeability at relatively lower temperatures and an improvement in embrittlement resistance.