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

Effects of tube fabrication variables on the oxidation of experimental Zr–2.5Nb tubes

“…In ZrNb alloys, several metallurgical factors have been suggested in controlling the oxidation resistance: equilibrium Nb content in a-Zr matrix [24], volume fraction of b-Zr phase [19], b-Zr alignment with oxide layer [25], and Nb content in b-Zr phase [13,19]. The effect of equilibrium Nb content in a-Zr on the oxidation resistance is the most prominent only in the case of quenched Zr-Nb alloy that has martensitic a 0 -Zr.…”

“…The effect of equilibrium Nb content in a-Zr on the oxidation resistance is the most prominent only in the case of quenched Zr-Nb alloy that has martensitic a 0 -Zr. Lin and DeLuca [25] measured Nb contents in a-Zr of Zr-2.5Nb tubes after heating these up to 500°C and reported that there was not substantial change in the Nb contents. The tubes used in the present experiment were not quenched in the final stage but stress-relieved at 400°C; therefore, the effect of Nb content in the a-Zr might be insignificant.…”

“…The tubes used in the present experiment were not quenched in the final stage but stress-relieved at 400°C; therefore, the effect of Nb content in the a-Zr might be insignificant. As for the volume fraction of b-Zr phase, there are controversial results; Urbanic and Griffith [19] demonstrated that corrosion increases with increasing volume fraction of b-Zr while others [25,26] reported that the corro- sion rate does not depend on the amount of b-Zr phase. Lin and DeLuca [25] raised the importance of b-Zr alignment in controlling corrosion rate but they concluded that the decomposition of b-Zr by heat treatment is more significant than the b-Zr alignment.…”

“…As for the volume fraction of b-Zr phase, there are controversial results; Urbanic and Griffith [19] demonstrated that corrosion increases with increasing volume fraction of b-Zr while others [25,26] reported that the corro- sion rate does not depend on the amount of b-Zr phase. Lin and DeLuca [25] raised the importance of b-Zr alignment in controlling corrosion rate but they concluded that the decomposition of b-Zr by heat treatment is more significant than the b-Zr alignment. It is generally known that the corrosion resistance increases with the decomposition of bZr, which accompanies Nb enrichment in the b-Zr phase.…”