Effect of Mo addition on the corrosion resistance of Zr-based alloy in water containing LiOH

As a sequel to the previous works on the mechanical properties and texture, the corrosion resistance of Mo-containing Zr-base alloys in LiOH-added water was studied. Experimental alloys of Zr–1Nb–1Sn–0.1Fe and Zr–1Nb–1Sn–0.1Fe–xMo (x=0, 0.2, 0.5 wt%), prepared by plasma arc remelting, showed lower weight gains than those of the commercial alloys including Zircaloy-4 and ZIRLO. Mo-addition resulted in a higher corrosion rate in the experimental alloys. Increased corrosion rate in these alloys was associated with lumpy microstructure of oxides with a higher portion of the monoclinic phase. The microstructural characteristic of oxides was attributed to the uneven distribution of β-Zr that was stabilized by Mo. Incomplete recrystallization and decreased normal basal texture also adversely affected the corrosion resistance of the Mo-containing alloys. It was shown, however, that the corrosion resistance of Mo-containing alloys could be improved to the level of the Mo-free alloy by a proper heat treatment to remove the undesirable microstructural feature.