类金刚石纳米薄膜的表面摩擦规律及磨损模型

Surface friction law and wear model of nanoscale diamond-like carbon film

为了研究类金刚石(Diamond-like carbon,DLC)薄膜的表面摩擦机制及磨损规律,首先通过对晶体碳高温熔化和快速淬火的方式,使用分子动力学模拟制备出DLC薄膜,然后利用半球形压头对薄膜表面进行摩擦刻划。制备得到的DLC薄膜密度为2.72g·cm-3,碳原子sp2、sp3杂化比例分别为37.1%和60.4%。摩擦结果表明,较低压力载荷下磨损率随着载荷力增加而线性增加,与宏观Archard模型一致;摩擦速度的不同会导致材料被加工表面应力分布及切削深度不同,造成磨损率随着摩擦速度的增加而下降,与实验结果相符;当薄膜含有Si原子夹杂且原子含量从0%增加至25%时,磨损率则先上升后下降。最后建立在压头固定载荷为50nN下描述摩擦速度、材料夹杂含量与磨损率三者关系的磨损模型,建立的磨损模型与仿真模拟相对误差在10%以内;利用模型得到在压头的载荷和摩擦速度不变时,薄膜磨损率最小值对应的Si夹杂含量为7.2%,这一模型为工程在线预测夹杂含量提供了较简单方便的手段。

In order to investigate the friction mechanism and wear law of diamond-like carbon（DLC）film,the DLC film was firstly prepared in the method of melting crystal carbon at high temperature and quenching it at rapid speeds based on molecular dynamics simulations.A hemispherical indenter was then used to perform friction behavior on the DLC surface.The prepared film has the density of 2.72 g·cm^-3,with sp2 and sp3 hybridization fraction of37.1% and 60.4% respectively.The friction results show that the wear rate increases linearly with the load under120 nN and this is in agreement with Archard＇s wear law.Whereas,the wear rate decreases with the friction velocity because of the effects of velocity on stress distribution and cutting depth.If Si atoms are embedded into the film as inclusion and the inclusion content increases from 0%to 25%,the wear rate will firstly decline and then rise.Finally a wear model among inclusion content,friction velocity and wear rate is established according to the wear datum under a certain load of 50 nN,with the relative error less than 10%to simulation results.The wear model indicates that the minimum wear rate occurs when the film has the Si content of 7.2% with a constant load and friction velocity.The wear model provides an efficient and convenient method for predicting inclusion content on line.