Enhancing wear and corrosion resistance of Al-Zn-Mg-Cu alloy via HVAF sprayed AlCrFe2Ni2(MoNb)0.2 high entropy alloy coating

One AlCrFe₂Ni₂(MoNb)_0.2 HEA coating is prepared on the 7A04 high-strength Al alloy substrate by the high-velocity air fuel spray technique to enhance surface performance. The coating exhibits a dense microstructure (0.245 % porosity) with dual-phase characteristics: (1) hot deformed particle regions retaining original B2/Laves phases and (2) severe plastic deformation regions featuring recrystallized nano-scale grains (∼80 nm), dislocations and dissolved B2/Laves phases. This bimodal microstructure originates from differential powder heating temperature during deposition. The coating exhibits a hardness of 605.9 HV_0.05, with a wear rate (5.39 ×10⁻⁵ mm³·N⁻¹·m⁻¹) two orders lower than the substrate (1.48 ×10⁻³ mm³·N⁻¹·m⁻¹) under identical wear conditions, primarily attributed to the load-bearing effect of hard phases in hot deformed particle regions. The predominant wear mechanism during the sliding wear test is fatigue wear, combined with abrasive wear and oxidative wear. The corrosion resistance of HEA coating is comparable to 316 L stainless steel, owing to the rapid formation ability of the passive film. However, micro-galvanic coupling between cathodic Laves phases and anodic BCC matrix in hot deformed particle regions promotes localized corrosion initiation. This work demonstrates an effective surface engineering strategy for improving aluminum alloy component protection performance in combined wear-corrosion environments.