Research On Laser Paint Removal Process For Aviation Aluminum Alloy Surface

In the aerospace field,coatings on aircraft skins can not only enhance corrosion resistance,but also increase the service life of the material.The coating has a useful life and will be damaged during service.At this time,the original coating needs to be removed and then resprayed.Laser cleaning technology has the advantages of flexible cleaning objects and no contact with material during cleaning.It has been widely used in different fields.With the development of laser cleaning technology and the increase in the types of cleaning objects,the requirements for the effect of laser cleaning and the surface quality after cleaning are gradually increasing.The cleaning mechanism and appropriate process parameters for different cleaning objects need to be more explicit,so it is particularly necessary to conduct in-depth research on the cleaning mechanism and cleaning process.At the same time,it is also one of the important research contents to analyze the surface quality after cleaning and the damage of the substrate to ensure that the laser cleaning can completely remove the contaminants and damage the substrate.In this paper,a nanosecond pulsed laser is used to carry out an experimental study on the laser cleaning of the aluminum alloy surface paint layer with an anodized film layer.The mechanism of laser paint removal and the influence of process parameters on the cleaning effect are analyzed and studied.The main research work is as follows:(1)By analyzing the theory of temperature rise and heat conduction after the paint layer is irradiated by laser,a three-dimensional heat conduction finite element model of the laser cleaning composite paint layer is established according to the actual situation.The temperature field distribution in the cleaning process is simulated by the finite element method,and the temperature field of the paint surface under different parameters is simulated.The mechanism of paint removal is further analyzed by the temperature distribution on the paint surface.At the same time,the evaluation method after cleaning is introduced.(2)The effects of laser energy density,laser scanning speed and laser spot overlap ratio on the cleaning effect are studied by changing the process parameters for laser paint removal experiments.The surface morphology analysis,thickness measurement and element composition detection are carried out on the surface of the cleaned samples to comprehensively study the influence of process parameters on the cleaning effect.The composite paint layer is cleaned by several sets of laser parameter combinations,and the variation law of surface roughness under different cleaning parameter combinations is analyzed.(3)The laser paint removal experiment is carried out by parameter combination,and the feasibility of laser layer-by-layer cleaning is analyzed.The elemental composition,cleaning thickness,and morphological characteristics of the cleaned surface are analyzed,and it is proved that the topcoat layer can be completely removed and a better primer layer can be obtained under the combination of parameters.In the experiment,the composite paint layer can be completely removed by a single cleaning,and the anodized film layer on the surface of the substrate is in good condition.The element composition and content,surface roughness,micro-morphology and surface Vickers hardness of the film layer are analyzed.The damage form and removal mechanism of the oxide film during excessive cleaning are studied.