CORROSION BEHAVIOR OF Zr(Fex, Cr1-x)2 ALLOYS IN 400℃ SUPERHEATED STEAM

Abstract

To study the corrosion behavior of second phase particles in zirconium alloys, Zr(Fex, Cr1−x)2 (x=1, 2/3, 1/3) metallic compounds which have the same composition as the second phase particles in Zr-4 alloy were prepared by vacuum non-consumable arc melting. XRD and energy filtered TEM were employed for analyzing the corrosion products, the element distribution and grain morphology after corrosion tests of Zr(Fex ,C r1−x)2 metallic compounds powder at 400 and 10.3 MPa superheated steam with different exposure times. The results show that Cr has a very strong effect on the corrosion resistance of Zr(Fex ,C r1−x)2 metallic compounds, increasing Cr content can improve the corrosion resistance. When Zr(Fex ,C r1−x)2 oxidation starts, zirconium oxide is formed while elements Fe and Cr are expelled from the zirconium oxide due to their low solid solubility in the oxide. α-Fe(Cr) and γ-Fe(Cr) are formed and then oxidized to the stable corrosion product (Fe, Cr)3O4. The different corrosion behaviors of metallic compounds will affect the microstructure evolution of zirconium oxide layer differently during the corrosion process, and hence affect the corrosion resistance of zirconium alloys.