Preparation of Al2O3/TiO2-containing Coating on Aluminium Alloys by Micro-arc Oxidation

TiO₂-containing ceramic coatings were deposited on the surface of aluminium alloys by micro-arc oxidition. Surface and cross-section topograph of ceramic coating were observed using scanning electron microscopy (SEM). The phase composition of ceramic coating was analyzed by X-ray diffraction (XRD). The results showed that ceramic coating surface became smoother, whereas micro pores decreased and outer loose layer became compact as under compact layer. The phase analysis of ceramic coating showed that it consisted of a mixed phase, which mainly contained ¿-Al₂O₃ (inner layer) and ¿-Al₂O₃ phase (outer layer) as well as a small quantity of Anatase and Al₂TiO₅. The outer mixed phase was compact and homogeneous. The wearing experiments indicated that TiO₂-containing ceramic coating had well antiwear behavior. The friction coefficient of ceramic coating in lubrication basically ranged from 0.20 to 0.30, which was lower than Al₂O₃ coating. It also indicated that Al₂O₃/TiO₂ coating had a tiny wearing capacity at a speed of 0.1 m/s and a load of 2 N in air.