| Aluminum alloy has high specific strength and good molding performance,which is the first choice material for aircraft,high-speed rail and other shells.Based on the requirements of anticorrosion and aesthetics,the surface needs to be coated with paint.In order to improving the interface bonding strength between the paint and the aluminum alloy substrate,it is usually necessary to texturize the surface of the substrate.Laser surface texture(LST),as a new surface treatment technology,can effectively roughen the substrate surface.In this paper,6061 aluminum alloy is used as the research object to explore the effect of LST treatment on the bonding strength of the interface between the SHF-2D epoxy zinc primer and the substrate.The main conclusions are as follows:(1)In terms of surface morphology.After LST treatment,comprehensive research and analysis were performed on the three-dimensional topography,surface roughness Ra,maximum contour height Rz and curve length Cl(bonding area).When the spot is not overlapped,it is found that when the power density is greater than 3.98×10~6 W/mm~2,thermal damage will occur,which lead to irregular circular spot,larger and rougher heat affected area,and the volume and quantity of sputtered material are increasing;It is found that with the increase of scanning times,the increasing value of spot depth is the same,but the process of sputter stacking at the boundary is similar to that of fluid melting;It is found that when the pulse width is 100 ns,the sputter at the spot boundary is"high-rise type",the surrounding sputter is the least,and the roundness of the spot is the best.When the spot is overlapped,It is found that when the column overlap rate of the spot is 0%,the spots in the row direction are externally tangent,and the sputters at the boundary are highly stacked.In addition,the roughness at the valley will decrease as the overlap rate of the column overlap rate increases;It is found that when the row overlap rate of the spot is 20%,the trough will be covered by the sputter of the boundary of the spot on the next column and row,and the surface of the substrate tends to be smooth(2)In terms of adhesion between SHF-2D epoxy zinc primer and substrate.LST can improve the adhesion of paint about 2-3 times,and the maximum adhesion can reach 15.98 MPa.Adhesion,surface micro-topography parameters,surface micro-topography after drawing and EDS analysis were comprehensively studied.When the spot is not overlapped,it is found that when the power density is greater than 3.98×10~6W/mm~2,the thermal damage will reduce the bonding force between the large particles and the matrix,resulting in poor substrate locking primer ability;It is found that with the increase of scanning times,the single spot becomes deeper,which makes it easier to lock the internal primer,causing the primer layer to break,reducing the adhesion area,resulting in poor substrate locking primer ability;It is found that when the pulse width is 100 ns,the above surface morphology greatly improves the adhesion.When the spot is overlapped,it is found that when the column overlap ratio of spot is 10%,the"upside down"sputter formed between adjacent spots in the row direction can effectively lock the primer,and the large particle sputter at the edge of spot has good substrate locking primer ability;It is found that when row overlap rate of spot is greater than 40%,micro-level pits and sputters will be formed on the surface of the substrate to improve the ability of the substrate locking primer. |
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