CORROSION BEHAVIOR OF Zr-Sn-Nb ALLOY

The corrosion behaviors of Zr-Sn-Nb alloy (N18,N36) developed in China have been studied by out-of-pile autoclave in 360℃ water with 70 μg/g Li,in 400℃ and 500℃ high pressure steam.The results show that the nodular corrosion for two kinds of alloys did not occur after 500h,and Zr-4 alloy did after 4h in high-pressure oxygen at 500℃;that the weight gain of N18 samples is lower than Zr-4,and of N36 is higher than Zr-4 after 245 days in 400℃ high pressure steam;that the weight gain for two kinds of alloys samples is only 16%-25% that of Zr-4 after 300 days in 360℃ water with 70 μg/g Li.N18 alloy possesses good corrosion resistance in both high temperature water and high pressure steam.Addition of alloying element Nb in Zr-Sn binary system,on the one hand,solid solution of Nb in α-Zr can resist the detrimental effect of C,N impurities on corrosion behavior,on the another hand,the formation of α-Nb second phase particles and their uniform distribution in alloy can reduce greatly the oxidation ratio in high temperature water and high pressure steam.The nonuniform growth of oxide film occurs at the oxide film/metal interface,and that of oxide film becomes more distinct after oxidant transition.