Study On Preparation And Dry Friction And Wear Properties Of Microarc Oxidation Ceramic Coaring On Aluminum Alloy

Air compressor is widely used at present,and the cylinder is the key parts of the air compressor,aluminum alloy due to light weight,high strength and easy processing molding has been fully replaced cast iron as the raw material for making the cylinder,However,many defects and deficiencies are exposed in the process of use.Due to the low surface hardness and poor wear resistance of aluminum alloy,the surface properties of aluminum alloy can be improved and the application range of aluminum alloy can be broadened by surface treatment.The effects of solution composition and positive and negative current density on the surface roughness,micromorphology,microstructure,hardness and friction and wear properties of the ceramic lay er were studied.The effects of ceramic layer thickness,load and material of friction pair on the friction and characteristics of micro-arc oxidation ceramic layer were also discussed.The results show that the addition of sodium tungstate and sodium tetraborate can reduce the oxidation voltage at the initial stage of micro-arc oxidation,improve the hardness of the ceramic layer,reduce the surface roughness of the ceramic layer,reduce the wear of the ceramic layer,and improve the wear resistance of the ceramic layer.The increase of forward current density can increase the singly discharge energy,increase the film forming rate and shorten the oxidation time.With the increase of negative current density,the micro-arc oxidation process is more stable,the discharge is unifonm,the surface of the prepared ceramic layer is smooth and the pore size is small.At the same time,the increase of the positive current density and negative current density can adjust the segregation phenomenon of solute ions in the solution and eliminate the dischaige concentration caused by the thickening of ceramic layer.The increase of the thickness of the ceramic layer will change the surface topography and increase the RMS deviation and steepness of the ceramic layer.With the increase of the thickness of the ceramic layer,the friction coeficient decreases and the wear quantity incteases,With the inicrease of the thicktess of the ceramic layer,the depth of the the furrow on the surface of the friction pair increases gradually,and serious abrasive wear occurs.The increase of the load will reduce the friction coefficient,reduce the wear amount,and the wear mark is also significantly narrowed.When the pair material is GCr15 steel ball,the wear amount of ceramic layer is small,the wear mark is wider,and abrasive wear occurs between them.However,when the pair is Si₃N₄ ceramic ball,the initial friction coefficient is larger,the wear of the ceramic layer is larger,the surface of the wear marks appears metallic luster,the ceramic layer has been completely worn and failed,and finally the adhesion wear of Si₃N₄ ceramic ball and the matrix occurs.