On the effects of heat treatment and surface orientation on corrosion and hydrogen ingress of Zr–2.5Nb pressure tube material

Abstract

The influences of surface orientation and heat treatment on the corrosion and hydrogen pickup of Zr–2.5Nb pressure tube material have been investigated. Following a prefilm treatment in 673 K steam and exposure to lithiated water (pH 10.5) at 583 K, the increase in oxide thickness and the pickup of hydrogen during a 120-day exposure at 583 K were monitored. In addition to being sensitive to the heat treatment given, the corrosion and hydrogen pickup were affected by the alignment of β-Zr with respect to the oxide surface. An enhanced oxide growth is associated with the initially undecomposed β-Zr aligned primarily perpendicular to the oxide surface. A minor effect on oxide growth is attributed to changes in the dislocation substructure due to heat treatment. A reduced hydrogen pickup is associated with β-Zr initially in the partially or fully decomposed states and aligned primarily perpendicular to the oxide surface.