Oxidation Properties of a Zirconium-2.7 w/o Niobium Alloy in the Temperature Range 650°–1000°C

The reaction kinetics and structures of the alloy/oxide composite system were determined for a Zr‐2.7 weight per cent Nb alloy exposed at temperatures over the range 650°–1000°C in oxygen at 1 atm pressure. These kinetics may be represented by a parabolic‐linear relationship. The zirconia scales contained small amounts of the intramolecular oxide, 6 ZrO 2 · Nb 2 O 5 . An investigation was carried out on the morphological development of the columnar scale and the underlying layer of oxygen stabilized α‐Zr plates in the β‐Zr alloy during parabolic oxidation. The sequence of the reaction product layers was consistent with predictions from the Zr ‐ Nb ‐ O phase diagram.