SiCw/AZ91镁基复合材料的微弧氧化行为及涂层的耐腐蚀性能

采用微弧氧化表面处理技术在SiCw/AZ91镁基复合材料表面制备保护性涂层.通过与AZ91镁合金对比,研究镁基复合材料的微弧氧化行为及其形貌特征,并采用电化学方法评价了微弧氧化涂层的耐腐蚀性能.结果表明,SiC晶须的存在影响了基底材料表面阻挡层的形成,使复合材料的微弧氧化行为不同于基体合金.与合金相比,在恒电流模式下进行微弧氧化的过程中复合材料的电压随时间的演变趋势不够理想,而且在相同工艺条件下复合材料的起弧时间比合金要长.复合材料在微弧氧化过程中偶尔会出现烧蚀现象.虽然SiC晶须会影响复合材料表面涂层的形成,微弧氧化处理仍然能够增强镁基复合材料的耐腐蚀性能,使其自腐蚀电位提高,腐蚀电流降低.当采用恒压模式制备涂层时,涂层耐腐蚀性能随电压的提高而增强.

MICROARC OXIDATION BEHAVIORS OF SiCw/AZ91 Mg ALLOY MATRIX COMPOSITE AND CORROSION RESISTANCE OF THE COATINGS

Protective coatings were fabricated on the surface of SiC_w/AZ91 Mg alloy matrix composite by microarc oxidation(MAO)surface treatment technique.Microarc oxidation behaviors of the composite were compared with AZ91 Mg alloy.The corrosion resistance enhancement of the composite after MAO treatment was also evaluated by electrochemical method.The results show that the microarc oxidation behaviors of the composite are different from those of the alloy because the presence of SiC whisker has influenced the formation of barrier film at the initial stage of MAO. Compared with the alloy,the composite doesn't exhibit ideal voltage evolution trend during MAO, especially at the early stage of MAO.For the composite,the time corresponding to occurrence of dielectric breakdown is longer than that of the alloy.Nonetheless,the corrosion resistance of the composite still is improved by the MAO coating.After the composite is coated by MAO,the corrosion current is decreased and the corrosion potential is increased.