Shao Wei, Shi Zhijun, Rao Lixiang, Zhang Silong, Xing Xiaolei, Zhou Yefei, Yang Qingxiang
State Key Lab of Metastable Materials Science & Technology, Hebei Key Lab for Optimizing Metal Product Technology and Performance, College of Materials Science & Engineering, Yanshan University, Qinhuangdao 066004, P. R. China.
College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, P. R. China.
Langmuir. 2020 Dec 22;36(50):15319-15330. doi: 10.1021/acs.langmuir.0c02765. Epub 2020 Dec 8.
With the development of the aerospace industry, the requirement for mechanical parts, which are serviced under extreme conditions such as high temperature, is more and more severe. Amorphous carbon (a-C) films are widely used in the aviation field as a protective coating because of their excellent antiwear and friction-reduction properties. However, a-C films are vulnerable to failure in a high-temperature environment, and a series of complex changes in the friction process make it a challenge to put forward the friction mechanism. Here, the sliding friction behaviors of amorphous carbon (a-C) films at different simulated temperatures (STs) (300-1300 K) were analyzed by molecular dynamics. The density, average coordination number, and local residual stress as well as the hybridization of sp, sp, and sp of a-C films were analyzed to reveal the high-temperature sliding friction mechanism of a-C films. The results show that the friction coefficient (μ) of a-C films increased with increase in ST. Meanwhile, the friction mechanisms of a-C films are different at an ST lower than 800 K and higher than 1100 K. Compared with those before sliding, the local residual stress of all a-C films is relaxed, which causes transformation of sp into sp. Moreover, when ST is lower than 800 K, the μ increased with increase in sp%. When ST is higher than 1100 K, the stability of a-C films is broken, which results in the rapid increase in μ.
随着航空航天工业的发展，对在高温等极端条件下服役的机械零件的要求越来越高。非晶碳（a-C）薄膜因其优异的抗磨损和减摩性能而在航空领域被广泛用作防护涂层。然而，a-C薄膜在高温环境下容易失效，并且摩擦过程中的一系列复杂变化使得提出摩擦机制成为一项挑战。在此，通过分子动力学分析了非晶碳（a-C）薄膜在不同模拟温度（STs）（300 - 1300 K）下的滑动摩擦行为。分析了a-C薄膜的密度、平均配位数、局部残余应力以及sp、sp²和sp³的杂化情况，以揭示a-C薄膜的高温滑动摩擦机制。结果表明，a-C薄膜的摩擦系数（μ）随ST升高而增大。同时，a-C薄膜在低于800 K和高于1100 K的ST下摩擦机制不同。与滑动前相比，所有a-C薄膜的局部残余应力均松弛，这导致sp³向sp²转变。此外，当ST低于800 K时，μ随sp²%的增加而增大。当ST高于1100 K时，a-C薄膜的稳定性被破坏，导致μ迅速增大。
