Oxidation behaviour of binary zirconium alloys containing intermetallic precipitates

To better understand the oxidation behaviour of Zr alloys, binary alloys containing 1 wt.% Fe, Ni, Cr or 0.6 wt.% Nb were oxidised in different oxidation environments at pressures ranging from 130 Pa to 10 MPa at 688 K and at different oxidation times. The surface of the oxidised alloys was analysed and the precipitate oxidation behaviour was found to be alloying element specific. Two different precipitate oxidation behaviours were observed in these alloys, precipitates with oxidation rates similar to the Zr-matrix (Fe and Ni) and others which show a delayed oxidation (Cr and Nb). In the case of Zr1%Fe pure iron oxide crystals of more than 1 μm size were observed at the surface of the material oxidised for longer oxidation times. In the oxide of Zr1%Cr and Zr0.6%Nb small crescent-shaped cracks were observed at the precipitate–oxide interface. In this study, materials oxidised for 110 days are examined in detail, and compared with those oxidised for lower pressures and/or shorter periods of time.