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

Specimens of V–4Cr–4Ti alloy were heated at 1273 K in vacuum, and the influence of this heat treatment on H2 absorption was examined at temperatures from 523 to 1023 K under the presence of water vapor of 10−5 Pa. The rate of H2 absorption was significantly reduced by the heat treatment in the temperature range examined. Such reduction in the absorption rate was ascribed to the surface segregation of Ti and increase in surface oxygen coverage caused by preferential oxidation of segregating Ti by water vapor. Comparison with data reported by other researchers [J. Nucl. Mater. 233–237 (1996) 376; Fusion Technol. 34 (1998) 868; J. Nucl. Mater. 233–237 (1996) 510] indicated the strong barrier effect of Ti oxide against hydrogen ingress.