| Abstract Scope |
Refractory alloys are of interest for aerospace applications due to their high melting points and strength at elevated temperatures. However, refractory metals are notorious for their poor oxidation resistance, as their single-cation oxides are non-protective. Recently, complex refractory oxides (e.g., TiNb2O7) have been proposed to be more protective. This work focuses on forming TiNb2O7 from the oxidation of alloys in the binary Nb-Ti system. Five Nbx-Ti(100-x) alloys (x=20, 34, 50, 60, 80 at%) were produced and oxidized in 1% O2-Ar at 1050°C for 20 h to explore the relationship between oxide scale and alloy composition. Micro x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize the oxide scales. All alloys but Nb80Ti20 formed TiO2 and TiNb2O7; Nb80Ti20 formed only Ti-Nb-O complex oxides. Alloy mass change (i.e., oxygen consumption) was found to increase with Nb content until a critical composition, in which mass change then decreased. |