Preparation And Wear-resisting And Corrosion-resisting Property Of Coatings On Different Silicon Content Aluminum Alloy By Microarc Oxidation

In order to solve the poor wear and corrosion properties an d make it resistant to corrosion and wear resistance demanded for aerospace and other applications more widely, this work prepared on a uniform surface corrosion-resistant ceramic membrane at high silicon content cast aluminum ADC12 with environmentally an d friendly and prepared on a uniform surface wear-resistant ceramic membrane at the low silicon content LD2 aluminum alloy by micro-arc oxidation.We will explore the method to produce the micro-arc oxidation film at the complex shape of aluminum alloy. The composition and structure of the coatings were characterized by thickness tester roughness tester, XRD, SEM, EDS and analyzes the influence of current density, duty cycle, frequency about coating structure and consisting.Electrochemic-al workstation and wear tester were used to test the coatings corrosion-resistant and wear-resistance,to explore the impact the film structure and composition of its corrosion and wear properties.Aluminum ceramic film thickness and roughness at high silico n content aluminum ADC12 increase with the current density and the duty ratio increase, decreases with increasing frequency. Coating phase mainly composed of γ-Al₂O₃ and small amounts of α-Al₂O₃, with the film presenting the surface pores and a few raised structure. The more dense and smooth and the smaller micro-porous,coatings have the better corrosion resistance.The corrosion-resistance of thick film, with high content of α-Al₂O₃ and less then the projection surface,is better.The best optimum parameters are 10 A/dm2, 50 %, 600 Hz, 40 min.Under these conditions, the film surface is uniform and compact.Ceramics thickness is of about 15 μm and roughness is of 0.52 μm, with a stable friction coefficient of about 0.2.The corrosion current is 1.253×10-8A/cm2, decreasing three orders of magnitude compared to matrix.Aluminum ceramic film thickness and roughness of low silicon content aluminum alloy LD2 increase with the current density, frequency and the duty ratio increase. The ceramic membrane phase mainly composed of α-Al₂O₃ and small amounts of γ-Al₂O₃.The film surface was "crater " morphology. The more uniform and dense surface layer and the thicker, the wear resistance of film is better. Optimum parameters are optimization for the current density of 10A/dm2, duty cycle of 50 %, frequency of 100 Hz and oxidation time 60 min. The ceramic membrane under the conditions is uniform and compact, with thickness of about 50μm and the coefficient of friction of 0.4.After sliding friction hardly 3000 m, film weight is not loss.Coating corrosion current was 7.930×10-9A/cm2, compared to the substrate to reduce three orders of magnitude.High silicon aluminum alloys at high frequency 600 Hz and low-silicon aluminum alloy in the low frequency 100 Hz prepared smooth dense ceramic membrane, preferably used for corrosion and wear environments.Ceramic membrane at complex aluminum surface can be prepared by method for cathode, uniformly and densely.