Surface reinforcement of magnesium alloy achieved via high entropy alloys/Al2O3 composite coating manufactured by middle-low temperature micro-particles deposition

With the increasingly wide application of Mg alloys, their surface reinforcements have become a research hotspot. This work aimed to deposit high entropy alloys (HEAs)/ceramic composite coatings on AZ91D surface using middle-low temperature micro-particles deposition (MLT-MPD). Fully dense HEAs/Al₂O₃ coatings were obtained, and the roles of parameters on the deposition characteristics were explored. Moreover, the mechanical and surface corrosion resistances of the coating were assessed via microhardness, nanoindentation, micro-scratch, wear and electrochemical tests. No oxidation or ablation was found on the AZ91D substrate after deposition. The microhardness of as-deposited AZ91D was reinforced to be ~380 HV, which is 5 times that of the substrate. In addition, the coating exhibited both good stiffness and a certain degree of toughness. As a result, the wear resistances of the as-deposited samples were improved significantly. The wear widths and depths were reduced from 1829.27 ± 31.53 μm to 1158.33 ± 71.04 μm and from 107.21 ± 2.57 μm to 26.73 ± 1.30 μm, respectively. Furthermore, the electrochemical corrosion potential (E_corr) was improved from −1558.8 mV to −1094.5 mV, and the passive current density (I_p) was reduced from 122 μA/cm² to 0.0806 μA/cm². This work provides a new approach for surface reinforcement of Mg alloys, which exhibits good application value.