DLCcoatings

DLC coatings, or diamond-like carbon coatings, are amorphous carbon films with a mix of sp2 and sp3 bonds, often containing hydrogen. They are not crystalline diamond but offer high hardness and low friction, useful for protective coatings. DLC is classified into subtypes such as hydrogenated amorphous carbon (a-C:H), tetrahedral amorphous carbon (ta-C) with high sp3 content, and nanocomposite DLC (nc-DLC). Properties depend on sp3 content, hydrogen, and microstructure.

Deposition is typically via plasma-assisted chemical vapor deposition (PECVD) or physical vapor deposition (PVD) methods, including cathodic arc, sputtering, or ion-beam deposition. ta-C often uses arc processes; a-C:H can be formed at lower temperatures. Adhesion layers (e.g., TiN or TiC) or graded interfaces are common to improve bonding to substrates.

Key properties include hardness (often 10–60 GPa), low friction (approximately 0.05–0.2 in dry sliding), and excellent wear and chemical resistance. DLC coatings are usually insulating or semiconducting, with properties varying by composition. They reduce wear and friction and can extend service life, but high residual stress and adhesion issues can cause delamination on some substrates.

Applications span automotive components (cam followers, valves), cutting tools, medical implants and instruments, bearings and gears, and protective coatings for read/write heads and other electronics components.

Design choices consider substrate compatibility, coating thickness, and deposition cost; surface pretreatment and adhesion-promoting layers are common.