异质a-C:H/a-C:H:F配副的摩擦学行为研究

Tribological Properties of a-C:H Sliding on a-C:H:F Films

目的研究F元素掺杂非晶碳基薄膜与a-C:H薄膜摩擦配副的摩擦学行为机制。方法利用PECVD法在Si基底上制备a-C:H:F薄膜,与直径为6.0mm的a-C:H薄膜摩擦对偶球组成摩擦配副体系,使用往复模式的CSMTRB3摩擦机研究a-C:H:F薄膜的摩擦学特性,频率为5Hz,滑动总次数为9000,外加载荷分别为2、4、6、8、10 N。通过纳米硬度、X射线光电子能谱、傅里叶红外光谱、激光共聚焦拉曼光谱、场发射扫描电镜及CSM摩擦试验机等,分别评价a-C:H:F薄膜的结构、表面形貌、力学性能、摩擦学性能等。结果在干摩擦环境下,随着载荷的增加,a-C:H:F薄膜的摩擦因数逐渐降低,平稳后摩擦因数低至0.018。通过掺杂F元素,一方面促进了薄膜的sp^(2)-C杂化,另一方面增大了薄膜的无序度。F元素具有钝化薄膜表面和静电排斥的作用,使得a-C:H:F薄膜具有较低的摩擦因数和磨损率。结论采用PECVD方法制备的a-C:H:F薄膜具有更好的减摩降损能力。

Reducing friction not only promotes the life and safety of the mechanical part,but also saves energy by lowing the friction force.Many films,like carbide,nitride and boride films,have been employed to reduce friction for moving parts.Among them,carbon based films have been thought to be the best choice due to their low friction,high anti-wear and high anti-corrosion properties,etc.However,these films are combined with sp^(2)and sp^(3)bonding structures and some times they are doped with hydrogen(H)or fluorine(F)or other elements,such as Si,P,Ti,Cr,etc.However,since H and F have single electrons that can terminate on the danglingσ-bond of amorphous carbon films to give repulsion force,contributing low friction.However,no one knows what will happen if the H and F doped amorphous carbon(a-C:H and a-C:H:F)films are taken to slide on each other.The work aims to study the tribological properties of a-C:H sliding on a-C:H:F film and explore the mechanism of tribology between the a-C:H and a-C:H:F films with the variation of loads.a-C:H:F film was prepared on Si substrate by plasma enhanced chemical vapor deposition and a-C:H film was deposited with magnetron sputtering of a carbon target in methane and argon atmosphere,respectively.Then,the tribology behaviors were evaluated on a commercial reciprocating ball-on-disk tribometer(CSM TRB 3 TRIBOMETER,Switzerland)with the test frequency and the total sliding times were 9000 at 5 Hz,respectively.Normal load was set to 2,4,6,8 and 10 N,respectively.Surface morphology of the a-C:H:F films were analyzed by SEM,and the mechanical properties were investigated by nanoindentation tests,with the depth no more than 1/10 of the a-C:H:F film thickness.The structure and tribology properties of the a-C:H:F films were tested by Raman spectroscopy,XPS spectroscopy and FTIR spectroscopy,respectively.Through this characterization results,it was found that the effect of fluorine doping played a key role in reducing friction coefficient as well as wear rate.The friction coefficient of a-C:H:F film decreased gradually and the curve was becoming stable with the increase of normal load,and the friction coefficients were 0.037,0.027,0.025,0.021,and 0.018,respectively.While the wear rates of a-C:H:F film reduced with increase of the load from 2 to 10 N,which were 1.991×10^(-8),1.212×10^(-8),0.881×10^(-8),0.721×10^(-8),0.557×10^(-8)mm^(3)/(N·m),respectively.The low friction coefficient can be ascribed to the transformation of sp^(3) to sp^(2) structure and promote the increase of sp2-C clusters in the film which can be proved by typical Raman spectrum.The low wear rate can be attributed to the wear debris,which prevent the direct contact of the a-C:H and a-C:H:F films.Fluorine also has effect of passivating film surface and electrostatic repulsion as hydrogen do.Generally,a-C:H:F films prepared by PECVD have a superior anti-friction and anti-wear ability to couple with a-C:H balls.