Regulation mechanism of graphene embedding depth on the mecha-nical and tribological properties of high-entropy alloy composite coatings

Incorporating graphene (Gr) into metallic matrices can enhance mechanical performance, yet its reinforcement efficiency strongly depends on spatial distribution, which remains insufficiently understood. This study employs molecular dynamics simulations to explore how different embedding depths (d) of Gr affect the nanoindentation and scratching behavior of CoNiCrFeMn high-entropy alloy (HEA) composites. The results show that Gr significantly increases the local hardness in the embedded region and alters the internal stiffness distribution of the alloy, thereby effectively regulating the plastic deformation and promoting rapid load dissipation. As the indentation load increases, the direct load-bearing capacity of Gr becomes the dominant factor contributing to the enhancement of indentation resistance. During scratching process, Gr embedding significantly reduces the friction force and exhibits depth-dependent wear resistance. An optimal depth of 20 Å achieves a 31.2 % reduction in friction coefficient and a 6.27 % decrease in wear atoms due to interfacial lubrication and elastic recovery. At 30 Å, the friction force reaches its minimum, and dislocation annihilation activity at the interface is significantly enhanced, contributing to improved fatigue resistance. These findings provide theoretical insight for designing and optimizing HEA-based composite coatings.