Novel method to fabricate aluminum nitride coatings on 2024-T3 aluminum alloy by high-frequency impact electrospark treatment

This study proposes a novel high-frequency impact electrospark treatment (HFIET) method to fabricate Al/AlN composite layers on 2024-T3 aluminum alloy substrates. The HFIET process utilized nitrogen as both the shielding gas and reactive nitrogen source for in situ synthesis of AlN, with precisely controlled discharge parameters to minimize substrate thermal damage. Analysis revealed a dense Al/AlN composite layer with near-stoichiometric composition (Al:N atomic ratio ≈ 1:1), confirmed by EDS and XRD. The microhardness profile exhibited a gradient distribution, decreasing from 450 HV at the surface to the substrate hardness (∼120 HV), attributed to the gradual reduction in AlN volume fraction from the top layer to the interior. Tensile tests demonstrated simultaneous improvements in ultimate tensile strength (∼10 % increase) and elongation (∼30 % increase) compared to untreated 2024-T3 alloy, indicating enhanced strength-ductility synergy. Corrosion resistance was significantly enhanced, and the Al/ AlN layer acts as an effective barrier against corrosive media infiltration, suppressing pitting initiation at the coating–substrate interface.