Preparation Al_2O_3/ZrO_2 composite coating in an alkaline phosphate electrolyte containing K_2ZrF_6 on aluminum alloy by microarc oxidation

摘要

Al_2O_3/ZrO_2 composite coating was prepared on 2A70 aluminum alloy by microarc oxidation (MAO) in a phosphate electrolyte containing K_2ZrF_6. The effects of K_2ZrF_6 in the electrolyte on the coating thickness, surface morphology, elemental composition and abrasive resistance were investigated. The results indicated that the MAO coating thickness increase due to the addition of K_2ZrF_6 in the electrolyte. In the electrolyte containing 6.0 g/L K_2ZrF_6, the coating was the most uniform and compact. The MAO coating formed in the electrolyte without K_2ZrF_6 was mainly composed of y-Al_2 O_3 and a little (X-AI_2O_3. Zirconium in the form of t-ZrO_2 was detected in the MAO coatings formed in the electrolyte containing K_2ZrF_6, and the Zr content increases with increasing concentration of K_2ZrF_6. A 7-Al_2O_3 and t-ZrO_2 nanocomposite coating was formed in the electrolyte containing 6.0 g/L K_2ZrF-6, and which exhibited the highest abrasive resistance.