Effects of tungsten addition on hydrogen absorption and permeation properties of Nb40Ti30Ni30 alloy

Tungsten was added to Nb40Ti30Ni30 alloys to investigate its effects on microstructure, hydrogen permeability and hydrogen absorption properties. Tungsten-added alloys consisted of a primary (Nb, Ti) phase and TiNi+(Nb, Ti) eutectic structure, although tungsten concentrated at the center of the primary phase. Tungsten addition did not change their hydrogen permeability. However, the hydrogen capacity decreased with increasing tungsten content, and 20% reduction of hydrogen capacity was attained by adding 5% tungsten. After annealing, tungsten was dissolved homogeneously in the primary phase, and segregation disappeared. The hydrogen permeability and capacity of the annealed alloy were 50% higher and 10% lower, respectively, than those of tungsten-free alloy. Thus, tungsten can reduce hydrogen capacity without degrading hydrogen permeability, which is expected to improve the resistance to hydrogen embrittlement.