High-Temperature Sliding Friction Behavior of Amorphous Carbon Films: Molecular Dynamics Simulation

Abstract

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 hightemperature 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 2 , and sp 3 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 3 into sp 2 . Moreover, when ST is lower than 800 K, the μ increased with increase in sp 3 %. When ST is higher than 1100 K, the stability of a-C films is broken, which results in the rapid increase in μ.

Effect of the Graphitization Mechanism on the Friction and Wear Behavior of DLC Films Based on Molecular Dynamics Simulations

“…Meanwhile, the mechanical properties of DLC films will change again. As a result, the interaction of T n and F f causes the film to change periodically. − Although there are thermal fluctuations, the late friction stage is still steady, and the DLC–DLC model can enter the steady state more quickly, as shown in Figure S1. In addition, the DLC-GR-DLC models have higher potential energies ( E p ) because they have more carbon atoms …”