Evaluation of Oxides Formed at High Temperature in Zr-2.5Nb Pressure Tubing

Abstract

The oxidation behavior of Zr-2.5Nb pressure tube samples has been studied at four different temperatures, i.e., 400°, 600°, 800°, and 1000°C.The oxide texture of (002)_m and (11 1)_m type increased with the temperature from 400°C to 600°C, however at temperatures above 600°C the texture strength seems to diminish and the oxide layer becomes structurally unstable. Further, the impedance response is found to be dependent on the microstructure of the oxide film. For the sample oxidized at 400°C, EIS spectra exhibited a two-time constant behaviour, showing the formation of two-layer oxide film on the Zr-2.5Nb alloy, which correspond to a porous outer oxide and a barrier inner oxide, respectively.