Role of Cr/CrN multilayer architecture in the wear behavior of DLC-based composite coatings

Diamond-like carbon (DLC) coatings possess a unique combination of low friction coefficient and high hardness, making them highly attractive for machining tool applications. However, their high intrinsic compressive stress often leads to brittle failure, limiting their practical use. In this study, a DLC-based composite coating was designed to enhance wear performance through the integration of a Cr/CrN multilayer architecture and the incorporation of Cr into the DLC top layer. Among all tested coatings, the DLC-based composite coating with a modulation period of 10 nm (M10) demonstrated strongest wear resistance, with a wear rate of 1.3 × 10 -6 mm 3 /N·m, representing a 59.3% improvement over the DLC-based composite coating with monolayer Cr interlayer (C0) and the lowest friction coefficient (∼0.1), approximately 75% lower than that of C0 coating at room temperature. The improved wear resistance exhibited by the M10 coating is attributed to its ability to dissipate strain energy through deformation rather than cracking. The thin sublayer structure restricts dislocation motion within individual layers, thereby enhancing hardness, while the high interface density promotes the nucleation of abundant stacking faults (SFs) in the CrN layers. By contrast, DLC-based composite coating with a modulation period of 100 nm (M100) exhibits limited strain energy dissipation via plastic deformation due to the sparse formation of SFs, ultimately leading to the development of surface ring-shaped cracks. Additionally, the Cr-DLC top layer undergoes a stress-induced transformation during nanoindentation, in which the amorphous Cr-DLC transitions into graphitic onion-like carbon (OLC) structures.