LAUSR

Abstract Micro-arc oxidation (MAO) ceramic coatings on the surface of aluminum alloy substrates with and without micro-groove have been successfully fabricated in the Na2SiO3-NaOH-EDTA-2Na solution. Microstructure characterization indicated that the micro-grooves on substrate surface could increase the content of α-Al2O3, γ-Al2O3 and 3Al2O3·2SiO2 phases and reduce the content of Al phase in the ceramic coating due to the sharp corner effect. EDS and XPS analysis showed that the content of Al and Si on the near outer surface of MAO coating on grooved substrate was more than that on non-grooved substrate. Meanwhile, MAO ceramic coating on micro-grooved substrate exhibited the faster growth rate in the initial stage of oxidation and the lower growth rate in the later oxidation. The final MAO coating showed the bigger micro pores and thicker oxidation film compared with that on the non-grooved substrate. Furthermore, the surface micro grooving pretreatment could dramatically improve the wear resistance and hardness of MAO coating, and the highest hardness of ceramic coatings of grooved substrate was around 1715 HV, which could be attributed to their special trapezoidal micro-groove structure.