High temperature oxidation of a Nb–Al–Si coating sputter-deposited on titanium

Abstract The oxidation behavior of an amorphous 58 Nb −38 A1 −4 Si (at.%) coating sputter-deposited on a titanium substrate has been studied in air at temperatures of 973–1173 K. The oxidation of the coated specimens follows a familiar parabolic rate law for a long time of oxidation at all temperatures examined, in contrast to the paralinear kinetics of uncoated titanium. Even though the coated specimen has higher oxidation rates than the amorphous Nb–Al–Si alloy itself, the amorphous Nb–Al–Si coating is highly effective in providing protection against the oxidation of titanium. The cross-sectional observation and energy-dispersive X-ray spectrometer analysis of the oxidized specimen reveal that titanium diffuses outward in the coating and is also present in the inner part of the oxide scale. The oxide scales formed on the coated specimens primarily consist of TiO2, AlNbO4 and κ -Al2O3. The presence of less protective TiO2 within the oxides appears to decrease the oxidation resistance of the coating, but is not significantly detrimental.