Abstract: The surfaces of Ti600 alloy,an advanced aircraft-engine material,were modified by micro-arc oxidization in NaAlO₂ solution.The influence of the NaAlO₂-concentration on the microstructures and tribological behavior was investigated with XRD,energy dispersive spectroscopy and scanning electron microscopy.The preliminary results show that the NaAlO₂-concentration had a major impact.For example,the oxidation voltage increased rapidly in the 1^st three minutes to the arcing voltage,at which small sparks showed-up,then,it slowly increased.As the NaAlO₂-concentration increased from 0.0 to 10 g/L,the arcing voltage and friction-coefficient decreased,the hardness and thickness increased,but the wear-rate changed in an increase-decrease manner; and the irregularly-shape porous oxides islands grew into continuous uniform coatings.Though the porous surface layer was rather loose,the compact interfacial layer exhibited strong adhesion.Formed at a NaAlO₂-concentration of 12 g/L,the fairly loose/porous oxides surfaces displayed a rather low wear-resistance.