Effect of h-BN nanoparticles incorporation on the anti-corrosion and anti-wear properties of micro-arc oxidation coatings on 2024 aluminum alloy

Abstract

Micro-arc oxidation (MAO) coatings are recognized for their protective capabilities, yet their inherent porosity and defects limit broader applications. In this study, we aimed to rectify these limitations and enhance their performance by integrating hexagonal boron nitride (h-BN) nanoparticles into the MAO coatings. This work investigates the influence of h-BN concentration on the structure and properties of MAO coatings on 2024 aluminum alloy substrate. The results indicate that h-BN integration diminishes porosity and roughness, while improving hardness, adhesion, and corrosion and wear resistance. The corrosion current density (Icorr) of the most effective composite coatings is approximately 1% of the 2024 aluminum alloy substrate and 10% of undoped MAO coatings. Wear tests demonstrate the significant self-lubricating effect of the h-BN distributed in the coating, with the coefficient of friction (COF) of the most abrasion-resistant coating after h-BN doping being 67% of the undoped coating. During MAO, h-BN is uniformly incorporated into the coatings via diffusion and electrophoretic migration. The two-dimensional structure of h-BN in the coatings effectively blocks micro-defects, delays corrosive substance penetration, and enables self-lubrication. Conversely, excessive h-BN concentrations can instigate agglomeration and performance degradation. Optimum corrosion resistance is achieved with an h-BN concentration of 2.5 g/L, while the best wear resistance is attained at 10 g/L. The study suggests that h-BN-doped MAO coatings present substantial potential for applications necessitating high corrosion and wear resistance in aluminum alloys.