偏压对DLC薄膜结构及摩擦学性能的影响

目的通过调节偏压,改善无氢DLC薄膜的微观结构,提高其力学性能和减摩抗磨性能。方法采用离子束辅助增强磁控溅射系统,沉积不同偏压工艺的DLC薄膜。采用原子力显微镜(AFM)观察薄膜表面形貌,采用拉曼光谱仪对薄膜的微观结构进行分析,采用纳米压痕仪测试薄膜硬度及弹性模量,采用表面轮廓仪测定薄膜沉积前/后基体曲率变化,并计算薄膜的残余应力,采用大载荷划痕仪分析薄膜与不锈钢基体的结合力,采用TRB球-盘摩擦磨损试验机评价薄膜的摩擦学性能,采用白光共聚焦显微镜测量薄膜磨痕轮廓,并计算薄膜的磨损率。结果偏压对DLC薄膜表面形貌、微观结构、力学性能、摩擦学性能都有不同程度的影响。偏压升高导致碳离子能量升高,表面粗糙度呈现先减小后增加的趋势,-400V的薄膜表面具有最小的表面粗糙度且C─C sp^3键含量最多,这也导致了此偏压下薄膜的硬度最大。薄膜的结合性能与碳离子能量大小呈正相关,-800 V时具有3.98 N的最优结合性能。不同偏压工艺制备的薄膜摩擦系数随湿度的增加,均呈现减小的趋势,偏压为-400V时,薄膜在不同湿度环境中均显示出最优的摩擦学性能。结论偏压为-400 V时,DLC薄膜综合性能最优,其表面粗糙度、硬度、结合力和摩擦系数分别为2.5 nm、17.1 GPa、2.81 N和0.11。

Effect of Bias on Structure and Tribological Properties of Diamond-like Carbon Films

The work aims to refine the microstructure and improve the mechanical properties and anti-friction and anti-wear properties of the hydrogen-free diamond-like carbon(DLC)films by adjusting the bias.Ion beam assisted magnetron sputtering system was used to deposit DLC films with different bias.The surface morphology was observed by atomic force microscope(AFM),microstructure was analyzed by Raman spectrometer,hardness and elastic modulus were tested by nano-indentation apparatus,change of substrate curvature before and after deposition was measured by surface profiler and residual stress was calculated,binding force between films and stainless steel substrate was investigated by large load scratch tester,tribological properties of films were evaluated by TRB ball-plate friction and wear tester and profile of the film wear marks was measured by white light confocal microscope and the wear rate of the film was calculated.The bias had different effects on the surface morphology,microstructure,mechanical properties and tribological properties of DLC films.The increased bias lead to the increase of carbon ion energy and the surface roughness firstly decreased and then increased.When the bias was-400 V,the surface roughness of the DLC film reached the minimum and the C─C sp^3 bond content was up to the maximum,which lead to the maximum hardness at this bias.The binding performance of the film was positively correlated with the carbon ions energy,and the optimal binding performance was 3.98 N when the bias was-800 V.The friction coefficient of the DLC film under different bias decreased obviously with the increased humidity.When the bias was-400 V,the DLC films showed the best friction properties in different humidity environment.When the bias is-400 V,the DLC film has the best comprehensive performance,and its surface roughness,hardness,binding force and friction coefficient are 2.5 nm,17.1 GPa,2.81 N and 0.11 respectively.