| AlSi12Cu alloy belongs to cast aluminum alloy series.It has the low density,low melting point,high performance,certain strength and corrosion resistance,were widely used in the automotive industry hub,aerospace,marine transport and other fields.However,it has low hardness,poor wear resistance.The corrosion resistance of the AlSi12Cu alloy does not meet the requirements in some medias,which restrict its application seriously.In order to improve the wear resistance and corrosion resistance of AlSi12Cu alloy,Micro-arc oxidation(MAO)technology was used to prepare aluminum oxide coating on the surface.The three parameters of current density,oxidation time and frequency were studied by orthogonal experimental.The surface morphology,element content and phase composition of the MAO coating were analyzed by Scanning Electron Microscopy(SEM)and its accompanying Energy Dispersive Spectroscopy(EDS)and X-Ray Dif-fraction(XRD),the corrosion and wear resistance were also analyzed and evaluated.In order to further improve the corrosion resistance of the coating,the MAO coating samples were sealed with different sealing agent and the effect of sealing treatment on the corrosion resistance of the MAO coating was studied.The main results are as follows:Through the above orthogonal experiments,the optimal process conditions were determined:the current density of 30 A/dm,the oxidation time of 20 min and the frequency of 600 Hz.In the optimal process conditions,the thickness of the MAO coating is about 15μm,consists of α-Al2O3 and γ-Al2O3,θ-Al2O3 and Al phase,the coating has excellent adhesion to the substrate.After the MAO treatment,the wear resistance of AlSi12Cu alloy was obviously improved,the friction coefficient was reduced from 0.64 to 0.37:The surface of’ the MAO aluminum sample was not appear obvious corrosion phenomenon after 240 hours of salt spray corrosion.However,the corrosion rate in the washing powder solution decreased 25 times more than that of the aluminum alloy substrate,showed that the corrosion resistance of AlSi12Cu alloy was improved by MAO treatment.The sealing treatment of the MAO coating was carried out with stearic acid and sodium silicate,respectively.The results show that the two sealing treatments can effectively fill the micro pores and the quantity of large pores on the MAO coating and the corrosion resistance was further improved.Among them,the sealing effect is better with stearic acid.The results of polarization curve analysis performed in 3.5%NaCl solution indicated.the corrosion current of the MAO coating after stearic acid sealing treatment decreased 100 times more than the substrate and the corrosion potential had a positive shift of 285 mV. |
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