Friction and Wear of the Ceramic Coating Formed on Magnesium Alloy

Abstract

Microarc oxidation is a recently developed surface treatment technology, by which ceramic coatings are directly formed on alloys, and the performances of the alloys are greatly improved. In this paper, a dense ceramic oxide coating was prepared on a AZ31 magnesium alloy by microarc oxidation in a Na2SiO3 electrolytic solution. The surface morphology, cross-sectional microstructure and phase composition were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The basic mechanism of microarc coating formation is explained. The friction and wear behavior of the micro-arc oxidation ceramic coating under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results show that the microarc oxidation coating is relatively dense and uniform, mianly composed of the loose layer, compact layer and transition layer. With elongated treated time, thickness of creamic coating increased obviously in the constant current condition. O, Si, Al and Mg element exist in the microarc oxidation ceramic coating, their distribution in the coating have been analysed too. The AZ31 magnesium alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface micro-arc oxidation ceramic coating experienced much abated adhesion wear and scuffing under the same testing condition. The micro-arc oxidation ceramic coating showed good friction-reducing and fair antiwear ability in dry sliding against the steel. 微弧氧化是最近开发的表面处理技术，通过该技术，陶瓷涂层直接在合金上形成，并且合金的性能得到极大改善。在本文中，在Na2SiO3电解液中通过微弧氧化在AZ31镁合金上制备致密的陶瓷氧化物涂层。使用扫描电子显微镜（SEM）和X射线衍射（XRD）分析表面形态，横截面微结构和相组成。解释了微弧涂层形成的基本机理。在球盘试验台上评估了微弧氧化陶瓷涂层在GCr15钢干滑动下的摩擦磨损性能。结果表明，微弧氧化膜相对致密，均匀，由松散层，致密层和过渡层组成。随着处理时间的延长，在恒流条件下，乳白涂层的厚度明显增加。微弧氧化陶瓷涂层中存在O，Si，Al和Mg元素，也分析了它们在涂层中的分布。 AZ31镁合金的特点是在干滑动下对钢的粘着磨损和磨损，而表面微弧氧化陶瓷涂层在相同的测试条件下经历了大大减少的粘附磨损和磨损。微弧氧化陶瓷涂层在对钢的干滑动中表现出良好的减摩性和良好的抗磨能力。