Corrosion Behavior of Zr-Nb Alloys in 360 ℃/20 MPa Water with Dissolved Oxygen

Early corrosion behavior of Zr-Nb alloys (M5 and E110) in 1.5 mg/L dissolved oxygen water was studied through a high temperature and high pressure (360 ℃/20 MPa) dynamic circulating water loop system. The microscopic characteristics of oxide films of two zirconium alloys, oxide film/matrix (O/M) interface characteristics and corrosion behavior of β-Nb phase near interface were analyzed by transmission electron microscopy (TEM). The results show that the thicknesses of the oxide films on the surface of M5 and E110 alloys reached 3.2 μm and 2.1 μm respectivly, after corrosion of 60 days. The corrosion of M5 alloy had already turned, while that of E110 alloy had not. The structures of O/M interface of the two alloys were very different. There was a ZrO transition layer at the O/M interface of E110, which was related to the slower growth rate of the oxide film. The β-Nb phases near the O/M interface in oxide films of the two alloys were partially oxidized, and dissolved oxygen (DO) could accelerate the oxidation of β-Nb phase.