A kind of composite coating using mixed powder of pure aluminum and pure titanium as feedstock was successfully deposited on orthorhombic Ti2AlNb alloy substrate by cold gas dynamic spraying. The ratio of pure titanium to pure aluminum of the powder was fixed at 1:3 in atom. The best parameters of the cold gas dynamic spraying experiment were obtained from analyzing the orthogonal table of spraying parameters when the density of coating was as evaluation criterion. The as-sprayed composite coating was heat-treated at 630 ℃ in flowing argon atmosphere for 5 h. The heating rate was controlled at 3 ℃/min and the flowing rate of the argon gas was kept at 40 ml/min. Analysis and characterization of sprayed and heat-treated coating were performed by means of scanning electron microscopy with EDS and image analysis system. X-ray diffraction was employed to investigate the structure changes between as-sprayed and heat-treated coatings. The coating’s mechanical properties, including micro-hardness and bonding strength were analyzed as well. It was found that the composite coating of the intermetallic compound TiAl3 and Al was formed and performed good bonding with the substrate after alloying heat treatment. The isothermal oxidation behaviors of orthorhombic Ti2AlNb complex alloy Ti751 and the alloy with TiAl3-Al coating was studied respectively at 950 ℃ in static air. The results indicated that oxidation kinetic curve of the Ti751 substrate with TiAl3-Al coatings was according to the parabolic law, and the surface oxide scale kept almost invariant and no crack was found at the interface of coating and substrate. The oxidation kinetic curve of Ti751 alloy substrate was increasing linearly, and the surface oxide scales were loose and porous, they are mostly TiO2 and little AlNbO4, and Al2O3. The high temperature oxidation resistance of the Ti2AlNb complex alloy Ti751 substrate with TiAl3-Al coatings was much higher than that of the naked substrate.
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