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

The influences of surface orientation and heat treatment on the corrosion a nd hydrogen pickup of Zr-2.5Nb pressure tube material have been investigate d. Following a prefilm treatment in 673 K steam and exposure to lithiated w ater (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 pic kup were affected by the alignment of beta-Zr with respect to the oxide sur face. An enhanced oxide growth is associated with the initially undecompose d beta-Zr aligned primarily perpendicular to the oxide surface. A minor eff ect on oxide growth is attributed to changes in the dislocation substructur e due to heat treatment. A reduced hydrogen pickup is associated with beta- Zr initially in the partially or fully decomposed states and aligned primar ily perpendicular to the oxide surface. (C) 1999 Published by Elsevier Scie nce B.V. All rights reserved.