Study on the Microstructure of DLC Films Regulated by Different Incident Energies and Their Microscopic Friction and Lubrication Mechanism in a Humid CO ₂ Environment

Friction and wear on key kinematic pair interfaces under extreme humid CO 2, heavy load and long-term service has become a critical bottleneck limiting the reliability and service life of aerospace equipment. Diamond-like carbon (DLC) films are regarded as the prime material for solving this problem due to their excellent tribological properties. Deposition incident energy is the most critical process parameter governing their microstructure and environmental adaptability. However, the atomic-scale friction and lubrication mechanisms of DLC films deposited at different incident energies in humid CO 2 environments remain unexplored. Therefore, this paper employs molecular dynamics simulations to investigate the tribological behavior of DLC films prepared at different incident energies in a humid CO 2 environment. The results show that with increasing incident energy, the film density increases and surface roughness decreases, accompanied by atomic mixing at the interface. The steady-state friction forces of DLC films prepared at different energies are similar, but high-energy films reach a steady state faster, with larger friction fluctuations and more severe wear during the running-in period. Furthermore, films prepared at high energy exhibit decreased permeability to medium molecules and weakened surface passivation, accompanied by more severe wear during the running-in stage. This study elucidates the atomic-scale regulation mechanism of incident energy on the frictional adaptation behavior of DLC coatings, which provides a theoretical basis for the engineering application of protective coatings for key aerospace kinematic pairs and is of great significance for overcoming the friction failure bottleneck of high-end equipment.