Oxidation behavior of Zr9S2 precipitates in Zr-0.8Sn-1.0Nb-0.3Fe-0.1Cr-xS alloys

Effect of trace sulphur (16-540 μg/g, S) on the corrosion resistance of zirconium alloys and oxidation behavior of Zr9S2 precipitates were investigated. Results show that S dissolved in α-Zr is among 63 ∼170 μg/g. Layered Zr9S2 particles precipitate when S addition reaches 170 μg/g. Zr9S2 precipitates oxidize easily and contribute to humps in the oxide films. Oxidation of Zr9S2 precipitates causes regular shaped cavities with nanometer size grains at the inner surfaces of oxide films. The presence of cauliflower-shaped humps at the inner surfaces of oxide films is also discussed.