Effect of SiC Nanoparticle Concentration on the Structural, Electrochemical, and Mechanical Properties of Plasma Electrolytic Oxidation Coatings on MA8 Magnesium Alloy

Abstract

The effect of silicon carbide (SiC) nanoparticles (NP) concentration on the morphological, electrochemical, and mechanical properties of coatings obtained by plasma electrolytic oxidation (PEO) on MA8 magnesium alloy was studied. The coatings were formed in a silicate-fluoride electrolyte containing β-SiC nanoparticles in concentrations from 0 to 10 g/L. An increase in the SiC concentration in the electrolyte led to an increase in the silicon and carbon content in the surface layer, which was accompanied by a change in the surface morphology and an increase in the heterogeneity of the coatings. An analysis of the electrochemical characteristics demonstrated the dependence of the coating properties on the SiC concentration. The coating formed at a concentration of 2.5 g/L showed the best protective properties (|Z|f=0.01 Hz = 5.8 × 105 Ω∙cm2). The maximum microhardness (3.9 ± 1.1 GPa) and the highest critical load values during scratch testing were obtained at a NP concentration of 5 g/L. Further increases in SiC concentration resulted in deterioration of the electrochemical and mechanical properties, consistent with increased structural heterogeneity. These results indicate that the concentration of SiC nanoparticles is a key parameter determining the performance properties of PEO coatings, and that moderate additions provide the most favorable combination of protective and mechanical properties under the studied conditions.

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