Effect of SiO2 Nanoparticles/Silicate on Characteristics of Micro-arc Oxidation Coating Formed on TC4 Alloy

Abstract:

TC4 micro-arc oxidation (MAO) coatings were prepared by adding SiO₂ nanoparticles or sodium silicate to the sodium meta-aluminate-based electrolyte. The effect of additives was investigated by XRD, SEM, EDS, electrochemical and wear tests. The results show that additives can considerably accelerate the formation of MAO coatings. The coatings are mostly composed of rutile and anatase TiO₂, α-Al₂O₃, γ-Al₂O₃, Al₂TiO₅ and SiO₂. Sodium silicate and SiO₂ nanoparticles added to the coating can effectively reduce the size of micropores and increase its thickness, whereas SiO₂ nanoparticles with superior physical properties can be directly deposited at the discharge channel, significantly increasing the coating's resistance to wear and corrosion. The coating with SiO₂ nanoparticles exhibits the best overall performance, with the lowest corrosion rate and average friction coefficient of 4.095×10^-5 mm/a and 0.30, respectively.