Effect Of Texture On Wettability And Tribological Properties Of Aluminum Alloy

In order to study the effect of surface texture and wettability on the tribological properties,the super-hydrophobic/oleophobic surface is constructed through building cone frustum and square dimples on the surface of 5083 warship aluminum alloy by laser processing,low-surface energy modification and coating SiO2 by sol-gel method.Based on Reynolds equation,a mathematical model of hydrodynamic lubrication of cone frustum and square dimpled surfaces is established,and the dimensionless average pressure of lubricating film is calculated to analyze the effect of surface texture on tribological properties theoretically.The main research contents and results are shown as follows:Super-hydrophobic/oleophobic aluminum alloy surface can be prepared by laser processing,low surface energy modification and coated with SiO2,the contact angles of water,sea water and oil droplets on the surface increased as the increment of the depth of dimple.The hydrophobic/oleophobic property of square dimpled surface is better than that of the cone frustum.The contact angles of water,seawater and oil on the surface with square dimple with the depth of 30?m are 163.3°,155.8° and 128.7°respectively.The adhesion between the droplets and surface changed by coating SiO2 and making the rolling angles of water and sea water droplets on the surface reduce to 2.1° and 3.5°.The friction test results show that the properties of antifriction and wear resistance of the super-hydrophobic/oleophobic surface of aluminum alloy enhanced significantly,the surface with dimple depth of 30 ?m has better properties of antifriction and wear resistance than that of 15 ?m,and the cone frustum dimpled surface is better than that of the square one.Compared with the smooth surface,the friction coefficient of textured surface with cone frustum dimple reduce by 30.5%,34.8%and 48.9%in water,seawater and oil lubrications,respectively.The friction coefficient in seawater is smaller than that in water while the wear loss has the opposite phenomena.The corrosion products of sea water reduce the friction coefficient,but increase the wear loss and have a double effect on the tribological properties.Calculation results of lubricating film show that,with the increase of dimple depth,the dimensionless average pressure of lubricating film increase first and then decrease.There is an optimal depth of 75 ?m which correspond the maximum dimensionless average pressure.The dimensionless average pressure of the cone frustum dimpled surface is 2.4 times larger than that of the square one.Therefore,the tribological performance of cone frustum dimpled surface is better than that of the square one,and the results of the tribological experiment are confirmed by the theoretical calculation.In order to optimize the tribological properties of the texture surface,the effect of the sliding direction,area ratio and of the dimple texture on dimensionless average pressure of the lubrication film is theoretically calculated.There is an optimal sliding direction of 0° corresponding to the maximum dimensionless average pressure of 1.47.When the depth to diameter ratio and area ratio of the cone frustum dimple texture are 0.3 and 55%,the dimensionless average pressure of the lubricating film reaches the maximum value of 10.1.When the depth to diameter ratio and area ratio of the square dimple texture are 0.35 and 63%,the dimensionless average pressure of the lubricating film reaches the maximum value of 8.1.