Research On Corrosion Resistance Of Laser Coeted Coating Of Aviation Aluminum Alloy

Aluminum alloy has been widely used in the aerospace field,and it is the main material used to manufacture aircraft skin.Friction stir welding(FSW),as a new green welding process,effectively solves the problem of difficult welding of aviation aluminum alloy.However,the corrosion resistance of friction stir welding seam is seriously lower than that of base metal,so it is necessary to carry out anti-corrosion treatment in this area.Laser cladding coating can prepare a dense anti-corrosion coating on the surface of the material,so this paper will prepare a dense Al₃Ti coating on the weld of aluminum alloy by this process to achieve the anti-corrosion effect on the weld area.The specific research contents and related conclusions to solve the above problems are as follows.Firstly,the high reflectivity of aluminum alloy restricts the application of laser technology in its modification.A two-step cladding method based on pre-sintering treatment is proposed in this paper,which improves the traditional laser cladding technology to some extent,effectively solving the problem that the solidification of powder spheres is not easy to pave and the coating is easy to crack when it is heated rapidly.Ansys finite element simulation software is used to simulate the phenomenon of coating warping and cracking in the process of cladding by traditional technology.The reason is that there is large thermal deformation and residual tensile stress concentration at the interface between powder layer and substrate.Based on the above laser technology,the influence of laser parameters on the quality of cladding coating was studied.The flatness and metallography of the coating were characterized by changing the laser power,scanning rate and track overlap rate.The results showed that the power was the decisive factor affecting the coating quality.When the power reaches 700W,the flatness quality of the coating surface will be greatly improved,but the influence range will gradually slow down when the power continues to rise.The metallographic structure of the coating prepared by the power near 700W is good,but when the power is insufficient,the Al₃Ti grain grows incompletely,while when the power is too high,the dilution rate is too high,and segregation substances increase.Then,the elements in different depths of the cladding coating are analyzed.From the EDS results,it can be inferred that the up-and-down convection of the molten pool will affect the element distribution.The influence of laser parameters and coating quality on the anti-corrosion effect of Al₃Ti coating was studied from two aspects:coating bonding effect and immersion corrosion test results.The bonding performance of the coating will affect the penetration rate of corrosive ions.The results of coating adhesion experiment show that the higher the laser power on the surface,the smaller the overlap rate of laser tracks,and the better the bonding effect of the prepared coating.However,the results of immersion test show that the corrosion resistance of weld samples without cladding coating is extremely poor,while the corrosion resistance of coatings prepared at 650W and 700W power is far better than that of other groups.Compared with other samples,this group has better corrosion resistance because of its small flatness,wide metallurgical bonding bandwidth and dense metallographic structure.To sum up,in this paper,through the improvement of laser cladding process,the quality characterization and surface integrity analysis of cladding coating,a set of methods for preparing Al₃Ti coating on friction stir welding seam of aluminum alloy was studied,and the influence of laser parameters and coating quality on corrosion resistance was explored through corrosion experiments.