硝酸铈添加剂对AZ91D镁合金微弧氧化膜组织与性能的影响

Effects of cerous nitrateadditive on microstructure and properties of MAO coatings on AZ91D magnesium alloy

为了进一步提高AZ91D镁合金表面的耐蚀性与耐磨性,在硅酸盐电解液体系中加入不同浓度的硝酸铈添加剂,利用微弧氧化(MAO)技术在其表面原位生长出陶瓷膜层。通过X射线衍射仪(XRD)和扫描电镜(SEM)对陶瓷膜层物相组成和表面微观形貌进行了表征,并通过电化学测试与摩擦磨损试验,评估了陶瓷膜层的耐蚀与耐磨性能。结果表明:硝酸铈添加剂的添加对膜层相组成影响较小,随着硝酸铈浓度的增加,膜层表面先出现较大孔径的孔洞,之后孔洞数量逐渐减少,且孔径也缩小。与无添加剂的膜层相比,硝酸铈的添加量为0.4 g/L时,其被磨穿时长从1 min增加到8 min,耐磨性有所改善;腐蚀电位从-1.69 V增加到-1.26 V,腐蚀电流密度从8.56×10^(-6)A·cm^(-2)降到2.49×10^(-7) A·cm^(-2),耐蚀性显著提高。

In order to further improve the wear resistance and corrosion resistanceof AZ91D magnesium alloy,the ceramic coating was in-situ formed on AZ91D magnesium alloy by applying micro-arc oxidation(MAO)technique in the silicate electrolytic liquid system with different concentrations of cerous nitrateadditive.The phase composition and surface microstructure of the coatings were characterized by X-ray diffractometer(XRD)and scanning electron microscopy(SEM).The corrosion resistance and wear resistance of the ceramic coatings were evaluated by electrochemical tests and friction and wear tests.The results show that the addition of cerous nitrate is of little effect on the phase composition of the ceramic film.With the increase of the concentration of cerous nitrate,the surface of the coating first appeared larger pores,and then the number of pores decreased,and the pore size became smaller.Compared with the MAO coating without additive,when the concentration of cerous nitrate is 0.4 g/L,the wear time increases from 1min to 8 min,and the wear resistance is improved.Its corrosion potential increases from-1.69 V to-1.26 V,and the corrosion current density is reduced from 8.56×10^(-6) A·cm^(-2) to 2.49×10^(-7) A·cm^(-2),thus the corrosion resistance is significantly increased.