Y(NO_(3))_(3)掺杂对AZ91D MAO涂层微观结构和耐磨性的影响

Effect of Y(NO_(3))_(3) doping on the microstructure and wear resistance of AZ91D micro-arc oxidation coating

本文中对AZ91D镁合金进行微弧氧化(MAO)改性处理,来获得具有较高耐磨性的陶瓷涂层,目标是提高AZ91D镁合金的耐磨性。在Na_(2)SiO_(3)-NaOH体系下引入稀土盐Y(NO_(3))_(3)掺杂,研究Y(NO_(3))_(3)掺杂量的变化对改性涂层相组成、微观结构、表面粗糙度、显微硬度以及摩擦因数的影响作用。结果表明:在Na_(2)SiO_(3)电解液体系下经微弧氧化处理后,镁合金涂层由MgO、MgSiO_(3)和Mg_(2)SiO_(4)等晶相组成,在掺杂Y(NO_(3))_(3)后涂层中MgSiO_(3)相含量有所增加。当Y(NO_(3))_(3)掺杂量超过0.015 mol/L时,微弧氧化涂层中典型特征“火山口状”的微孔通道明显减少,涂层表面趋于光滑。当Y(NO_(3))_(3)浓度过高时,涂层中局部区域出现腐蚀坑。经微弧氧化改性处理后涂层的显微硬度均比基体合金高,尤其当Y(NO_(3))_(3)掺杂量超过0.015 mol/L时,涂层显微硬度值最大,约为382.6±7.6 HV_(1),达到基体硬度4倍以上。Y(NO_(3))_(3)掺杂涂层的摩擦因数先降低后增加,最小值出现在试样S3时,摩擦因数约为0.60~0.65,耐磨性提高。

In this paper,AZ91D magnesium alloy is modified through micro-arc oxidation to obtain ceramic coating with high wear resistance.The aim is to improve the wear resistance of AZ91D magnesium alloy.The effect of the change in Y(NO_(3))_(3) doping amount on phase composition,microstructure,surface roughness,microhardness and friction coefficient of the modified coating is studied by introducing rare earth salt Y(NO_(3))_(3) doping into Na_(2)SiO_(3)-NaOH system.The results show that the magnesium alloy coating is composed of MgO,MgSiO_(3) and Mg_(2)SiO_(4) after the micro-arc oxidation treatment in the Na_(2)SiO_(3) electrolyte system,and the phase content of MgSiO_(3) in the coating increases after the doping of Y(NO_(3))_(3).When the doping amount of Y(NO_(3))_(3) exceeds 0.015 mol/L,the typical“crater-like”micro-pore channels in the micro-arc oxidation coating significantly reduces,and the coating surface tends to be smooth.When the concentration of Y(NO_(3))_(3) is too high,corrosion pits appear in local areas of the coating.The microhardness of the coating after modification by micro-arc oxidation is higher than that of the matrix alloys,especially when the doping amount of Y(NO_(3))_(3) exceeds 0.015 mol/L.During these periods,the microhardness of the coating is the highest at about 382.6±7.6 HV 1,which is more than 4 times the hardness of the matrix.The friction coefficient of the Y(NO_(3))_(3) doped coating decreases first and then increases,and,when the minimum value appears in sample S3,the friction coefficient is within 0.60 to 0.65,which proves an improved wear resistance.