Effect of SiC addition in electrolyte on the microstructure and tribological properties of micro-arc oxidation coatings on Al-Mg-Sc alloy

Abstract

sHard and wear-resistant ceramic coatings with SiC nanoparticles were in situ fabricated on Al-Mg-Sc alloy using micro-arc oxidation (MAO) method in alkaline silicate electrolyte. The microstructure, roughness, and composition of the MAO coatings were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) and laser scanning confocal microscopy (LSCM), respectively. The microhardness of the MAO coatings was obtained microhardness tester. The wear resistance of the MAO coatings was evaluated by ball-on-disc reciprocating tribo-tester. The results showed that the phase composition of the obtained coatings with the typical pancake-like stacking structures was mainly composed of α-Al2O3 and γ-Al2O3. the porosity and roughness gradually decreased with the increment of SiC nanoparticles concentration. Al content gradually decreased from the matrix to the outside, while the Si content gradually increased. The incorporation of SiC nanoparticles further increased the microhardness of the MAO coating. Especially in alkaline silicate electrolyte with 1.5g l−1 SiC nanoparticles, the microhardness could reach 1270 HV0.5. The friction coefficient of the MAO coatings prepared in electrolyte solution with SiC addition varied from 0.4 to 0.55, and the ceramic coating with 1.5g l−1 SiC nanoparticles exhibited the best wear resistance. The wear mechanism was attributed to be the combination of abrasive wear, adhesive wear and oxidation wear.