Intermetallic compounds of zirconium and their influence on the corrosion properties of zirconium alloys

1. It was established that the corrosion of pure intermetallic compounds (ZrFe2, ZrMo2, Zr2Ni, Zr4Sn, Zr2Cu) in the temperature interval 400–800°C occurs at a higher rate than that of pure zirconium, both in oxygen and in water vapor. 2. The least rate of oxidation is possessed by the intermetallic compound ZrMo2, the greatest by the intermetallic compound Zr2Ni. The intermetallic compound Zr4Sn has a low rate of oxidation at 300–400°C, but with increasing temperature the rate of its oxidation rises sharply. 3. A relationship was detected between the kinetics of the oxidation, structure, and composition of oxide films arising on the surface of intermetallic compounds. The high corrosion resistance of the intermetallic compound ZrMo2 is due to the formation of a homogeneous oxide film on its surface, consisting of the compound ZrMo2O5. The catastrophic oxidation of the intermetallic compound Zr2Ni is explained by the two-phase structure of the film and its cracking during growth. On the intermetallic compounds ZrFe2, Zr2Ni, and Zr2Cu oxide films are formed, the surface layers of which consist entirely of the oxides Fe2O3, NiO, and Cu2O, respectively, while the deeper layers consist of a mixture of the indicated oxides and ZrO2. 4. It was shown by the method of measuring the microhardness during heating that the intermetallic compounds Zr2Ni, Zr4Sn, and Zr2Cu become weakened in the interval 350–450°C, whereas the intermetallic compounds ZrMo2 and ZrFe2 retain their original hardness up to 700°C.