Surface characteristics and oxidation behavior of nitrogen ion-implanted Zr–Sn–Nb alloy

The surface characteristics and oxidation behavior in air at 500 °C of Zr–Sn–Nb alloy have been investigated. Zr–Sn–Nb specimens were implanted by nitrogen ions with a dose range from 5 × 1016 to 4 × 1017 ions/cm2 and then oxidized in air at 500 °C for 120 min. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase formation of nitrogen ion-implanted samples and phase transformation in the oxide films. The depth profile of the oxides in the scale was analyzed by Auger electron spectroscopy (AES). Nitrogen implantation into Zr–Sn–Nb alloy resulted in the precipitation of ZrN and the depth profiles confirmed the formation of ZrN. Microhardness measurements revealed an increase after nitrogen implantation into the samples. The measurement of weight gain showed that a significant improvement was achieved in the oxidation behavior of nitrogen ion-implanted Zr–Sn–Nb compared with that of the as-received Zr–Sn–Nb. The addition of nitrogen changed the phase in the scale from monoclinic ZrO2 to tetragonal ZrO2. The mechanism of the improvement was discussed.