镁锂合金表面含碳陶瓷层的摩擦性能

通过在Na₂SiO₃-KOH基础电解液中加入石墨烯添加剂,在镁锂合金表面制备出一层自润滑的含碳陶瓷层. 利用扫描电镜、原子力显微镜以及X射线衍射仪分析了陶瓷层的表面形貌、粗糙度以及物相组成,利用摩擦磨损试验仪对陶瓷层在室温下的摩擦学性能进行研究. 其结果表明,加入石墨烯后制备出的含碳陶瓷层表面放电微孔分布均匀,且其微孔尺寸和表面粗糙度均明显降低. 相比于镁锂合金,陶瓷层的表面硬度也得到明显的提高. 此外,含碳陶瓷层主要由SiO₂、Mg₂SiO₄以及MgO物相组成,而石墨烯则以机械形式弥散分布于陶瓷层中并起到减摩作用. 当石墨烯体积分数为1%时,陶瓷层表面显微硬度为1317.6 HV_{0.1 kg},其摩擦系数仅为0.09,其耐磨性明显提高. 同时,陶瓷层磨痕的深度和宽度均明显小于镁锂合金,而且较为光滑,表明陶瓷层表面没有发生严重的黏着磨损. 

Friction properties of C-containing ceramic coatings on an Mg-Li alloy

Due to its specific strength, superior electromagnetic shielding and excellent processing capabilities, the magnesium-lithium (Mg-Li) alloy is regarded as one of the most promising structural metal materials and has been extensively applied in various fields such as aerospace, offshore engineering, and the communication industry. Unfortunately, inferior tribological behavior, caused by low hardness, a fluctuating friction coefficient, and serious adhesive wear, has severely inhibited large-scale application of Mg-Li alloys in industrial engineering. Therefore, in this study, to enhance the tribological performance of a micro-arc oxidation (MAO)-produced ceramic coating on an Mg-Li alloy, a variety of inorganic particles were tentatively added to MAO electrolytes to prepare composite ceramic coatings with pronounced friction and wear resistance properties. MAO in Na₂SiO₃-KOH electrolytes with graphene additives was used to produce self-lubricating C-containing ceramic coatings on an Mg-Li alloy. The surface morphologies, roughness, hardness, and phase compositions were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), a Vickers hardness test, and X-ray power diffraction (XRD). At room temperature, the tribological properties of the ceramic coatings were evaluated by friction and wear tests. The results indicate that the micro-pores in the C-containing coatings distribute uniformly on the alloy surfaces and a significant decrease in micro-pore size and surface roughness is observed. The surface hardness of the coatings show significant enhancement compared with that of the Mg-Li alloy. The coatings mainly consist of SiO₂, Mg₂SiO₄, and MgO phases; graphene is dispersed throughout via mechanical effects and displayed an antifriction effect. The C-containing coating produced when the volume fraction of graphene in the electrolyte is 1% show good wear resistance and its surface hardness and friction coefficient are 1317.6 HV_{0.1 kg} and 0.09, respectively. Meanwhile, compared with the Mg-Li alloy the wear traces on the coating appears narrower and shallow, and the worn area seems relatively smooth, which indicates that slight adhesive wear occurs on the C-containing coating surface.