Properties Of Ceramic Composite Coatings Synthesized On An Aluminium Alloy Surface By Plasma Electrolytic Deposition

Insufficient wear resistance and corrosion resistance remain contributing factors that limit the application of aluminium alloys.In order to modify the surface propperties of aluminum alloys,cathodic plasma electrolytic deposition（CPED）and plasma electrolytic oxidation（PEO）was used to prepare protective coatings in this thesis.In electrolyte of glycerol/urea/disodium hydrogen phosphate and glycerol/urea/zirconium/disodium hydrogen phosphate,AlPO₄-Al₂O₃and AlPO₄-Al₂O₃-ZrO₂ thick ceramic coatings were successfully synthesized seperately on an aluminium alloy surface by combining cathode plasma electrolytic deposition and plasma electrolytic oxidation.The thickness of AlPO₄-Al₂O₃ coating reaches 125μm,and the AlPO₄-Al₂O₃-ZrO₂ coating,131μm.The AlPO₄-Al₂O₃ coating shows significant wear resistance,with its wear rate of 0.79×10^-4 mm³/N·m which is 22.5%and 29.4%lower than that of the coating prepared by CPED and PEO,respectively.However,the AlPO₄-Al₂O₃-ZrO₂ coating exhibits excellent corrosion resistance during immersion in 3.5%NaCl solution.At|Z|_{f=0.1 Hz},the impedance modulus can be 2.5×10⁶Ω·cm²,which is one and two orders of magnitude higher than that of the coating prepared separately by CPED and PEO.After immersion at 168h,the impedance modulus can still reach 3.5×10⁵Ω·cm² at|Z|_f=0.1Hz,and the corrosion resistance of the coating is significantly improved.