离子液体润滑下非晶碳膜的载流摩擦磨损行为

Current-carrying Friction and Wear Behavior of the Amorphous Carbon Film Lubricated by Ionic Liquid

目的考察非晶碳膜(amorphous carbon film,a-C)在干摩擦和在离子液体(IL)润滑下的载流摩擦磨损行为特点。方法选取不锈钢、涂覆离子液体的不锈钢、a-C薄膜和涂覆离子液体的a-C薄膜(a-C-IL)分别与不锈钢小球对磨,在直流电流为0.2 A的条件下进行摩擦磨损测试,对比了各种试样的摩擦学行为。通过扫描电镜、表面三维轮廓仪和拉曼光谱对磨痕和磨斑进行分析表征,并讨论各种摩擦副的磨损机制。结果非晶碳膜与离子液体均能有效地降低钢-钢摩擦副在载流条件下的摩擦系数,使得稳定摩擦系数从～0.8分别降低到～0.2和～0.15。当a-C膜与IL进行复合后,进一步降低了a-C膜的载流摩擦系数(～0.1),但是a-C膜的耐磨性能降低。结论在载流摩擦磨损测试下,钢-钢摩擦副的摩擦系数大,磨损严重,伴随轻微的粘着磨损;离子液体可以明显减小摩擦副之间的粘着,降低钢-钢摩擦副的摩擦系数和磨损率。在钢基底上镀a-C薄膜,摩擦过程中a-C磨屑形成的转移膜发生了石墨化,能显著降低摩擦系数,减小磨损率。a-C-IL固液复合薄膜具有比a-C膜更低的载流摩擦系数,但其耐磨性能不如a-C膜。

The work aims to investigate the current-carrying friction and wear behaviors of the amorphous carbon(a-C) film in both dry friction and ionic liquid(IL) lubricated conditions. The friction tests were carried by grinding stainless steel, steel coated with IL, a-C film and a-C film coated with IL(a-C-IL) with stainless steel balls under direct current of 0.2 A to compare the friction behaviors of various samples. The wear traces and wear scars of the samples were characterized by scanning electron microscopy, surface 3 D profiler and Raman spectrum, and the wear mechanisms of the friction pairs were discussed. Both the a-C film and IL could effectively decrease the current-carrying friction coefficient of the steel-steel friction pair, and reduce the steady friction coefficient values to ~0.15 and ~0.20 from ~0.8, respectively. The composite lubrication of the a-C and IL further decreased the current-carrying friction coefficient(~0.1), but the wear resistance decreased accordingly. The friction coefficient of the steel-steel friction pair is high and the wear is severe. The mechanism is severe abrasive wear with slight adhesion wear.The IL lubrication can obviously reduce the friction coefficient and wear rate of steel-steel friction pair, and the wear mechanism is acceptable abrasive wear. The a-C film can provide good lubrication and wear resistance for the electrical contact material in dry friction. In the current-carrying friction process, the formed transfer film by the a-C wear debris is graphitization and the mechanism of the a-C films is slight abrasive wear. The friction coefficient of the a-C-IL solid-liquid composite lubrication coating is lower than that of a-C film, but the wear resistance is weaker. In friction process, the surface structure of the a-C is broken, and the generated wear debris mixed with the IL can form a solid-liquid composite lubrication coating, which can reduce the friction force, but is easily extruded out of the friction contact zone. Therefore, a steady solid-liquid composite lubrication coating needs to be reconstructed with more wear debris worn off from the a-C film to increase the wear rate.