AZ91HP镁合金电沉积Ni-SiO2纳米复合镀层的显微结构与耐磨性

摘要

以AZ91HP镁合金为研究对象,以纳米氧化硅为第二相粒子,通过纳米复合电沉积法制备AZ91HP镁合金Ni-SiO2纳米复合镀层.利用扫描电镜观察纳米复合镀层的显微形貌与微观结构,利用显微硬度计测定纳米复合镀层显微硬度,利用M-200摩擦磨损试验机测试纳米复合镀层的耐磨性能.结果表明:在AZ91HP镁合金表面获得了结晶均匀、结构致密的Ni-SiO2纳米复合镀层；纳米复合镀层剖面形貌显示纳米复合镀层与镁合金基体结合良好；镀液中纳米颗粒含量为10 g/L时,AZ91HP镁合金表面电沉积Ni-SiO2纳米复合镀层的显微硬度最高,最高达HV367；摩擦磨损试验表明纳米复合镀层与镀镍层、镁合金基体相比,耐磨性明显提高,这是由于纳米颗粒的细晶强化和弥散强化所致；纳米复合镀层的磨损机制主要是磨粒磨损,镁合金基体磨损机制为粘着磨损,镀镍层磨损机制为剥层磨损.%The Ni-SiO2 nano-composite coatings were fabricated by electrodeposition on the AZ91HP magnesium alloy surface,in which nano-SiO2 was chosen as the second-phase particulates.The microstructure was observed by SEM,the microhardness was measured by micro-density tester and the wear resistance was estimated by M-200 type block-on-wheel dry sliding frication and wear tester.The results indicate that the Ni-SiO2 nano-composite coatings with uniform crystalline,dense structure can be obtained on AZ91HP magnesium alloy.The interface morphology shows that the combination between the nano-composite coatings and magnesium alloy is fine.The maximum value of microhardness reaches HV367 when the content of nanoparticles is 10 g/L,however,the microhardness of the pure nickel coatings is HV274 and the hardness of magnesium alloy only is HV82.7.The frication and wear experiments reveal that the wear resistance of nano-composite coatings are improved obviously compared to magnesium alloys and pure nickel coatings,which are induced by dispersive strengthening effect and grain refining effect.The main wear mechanism of nano-composite coating is abrasive wear,the wear mechanism of magnesium alloys is adhesion wear,and that of pure nickel coating is exfoliation wear,respectively.