Surface and tribological characterization of anodic aluminum oxide coating containing diamond-like carbon flakes

The incorporation of carbonaceous material like graphite into anodic aluminum oxide coatings offers excellent mechanical properties and low friction due to its self-lubricating behavior. However, the coating containing graphite has poor durability and surface quality, such as the formation of submicron cracks on the surface, which limit its use in a load-bearing application. These limitations encouraged the study of diamond-like carbon (DLC) performance in the aluminum oxide matrix since DLC consists of sp2-bonded carbon of graphite-like structure and sp3-bonded carbon of diamond-like structure. Since DLC usually exists as a thin film, it was deposited on copper particles that act as a carrier. As an effective approach to improve sliding properties, annealing heat treatments were conducted at temperatures ranging from 100 °C to 500 °C for 1 min holding time. AA2017-T4 aluminum alloy was anodized with 1 g/L of untreated and hear-treated DLC deposited on copper (Cu) particles, respectively, at a constant current density of (15 A/dm2) and fluctuant voltage (±15 V). Then, morphological, chemical composition, surface hardness, and tribological properties were evaluated. Results showed that the incorporation of DLC showed a significant reduction in porosity and microcracks and increase surface hardness compared to conventional oxide coating. The oxide coating with heat-treated DLC showed better sliding properties than untreated DLC due to more sp2 graphite phase formed as a lubricating layer and helped to reduce friction and wear at sliding contact interfaces. [Display omitted] •The present study investigated the potential of DLC to be used as reinforcement in composite anodic aluminium oxide coating.•DLC was deposited on copper particles before incorporated into the anodic oxide coating.•The friction coefficient for Al2O3 coating with preheated DLC shows reduction, and the wear-resistant also increased.