Abstract:Ceramic coating was deposited on TiAl alloy substrate by micro-arc oxidation (MAO) in a silicate-aluminate electrolyte solution with additives including sodium citrate, graphite and sodium tungstate. The microstructures and compositions were analyzed by SEM, EDX and XRD．The corrosion and wear properties of the coatings were investigated by potentiodynamic polarization and ball-on-disc wear test, respectively. The results show that the MAO coatings consist of WO₃, Ti₂O₃, graphite and Al₂O₃ besides Al₂TiO₅ and Al₂SiO₅. With additives in the electrolyte, the working voltage at the micro-arc discharge stage decreases, and the ceramic coating gets smoother and more compact. The corrosion current density of MAO coating is much lower than that of TiAl substrate. It can be reduced from 9.81×10^{−8 A/cm2} to 3.02×10^{−10 A/cm2}. The MAO coatings composed of hard Al₂O_3, WO₃ and Ti₂O₃ obviously improve the wear resistance of TiAl alloy. The wear rate is −3.27×10^{−7 g}/(N∙m).

Key words: TiAl alloy; micro-arc oxidation coating; additive; corrosion resistance; wear resistance