Effects Of Laser Cleaning Process Parameters On Surface Characteristics And Wear And Corrosion Resistance Of 7075 Aluminum Alloy

As a kind of hard aluminum alloy,7075 aluminum alloy is often used in the field of aerospace and automobile manufacturing because of its light weight,easy processing,good corrosion resistance and strong impact resistance.A layer of oxide film will be formed on the surface of 7075 aluminum alloy after manufacturing.The existence of this oxide film will reduce the strength and toughness of aluminum alloy weld,the conductivity of electric lap joint,the bonding quality of electrodeposited coating on aluminum alloy surface and the quality of equipment maintenance.Therefore,the oxide film needs to be removed in advance in these occasions.Compared with the traditional cleaning method,laser cleaning has the advantages of green cleaning,high precision and automation.In this paper,the laser cleaning technology was used to clean the surface of 7075 aluminum alloy.The effects of different laser cleaning process parameters on the surface characteristics,friction properties and corrosion behavior of 7075 aluminum alloy before and after cleaning were studied.The main work of this paper is as follows:(1)The effects of different laser average power,scanning speed of galvanometer and cleaning times on the surface morphology,oxygen content,phase composition,microhardness and roughness of 7075 aluminum alloy after cleaning and the reasons for the changes were explored.It is concluded that when the average laser power is 140 W,the scanning speed is3500mm/s and the cleaning times are 1,there is no serious melting phenomenon on the cleaned surface,and the mass percentage of oxygen is low,which is 1.16%.Too large average laser power,too small scanning speed and too many cleaning times will cause serious ablation and thermal oxidation of the cleaned surface,and the severely ablated molten layer will increase the surface roughness.Laser cleaning has little effect on the surface microhardness of 7075 aluminum alloy.Compared with the original surface,the surface microhardness after cleaning is increased by 13.4 HV at most.(2)The wear behavior and wear resistance of the cleaned surface were analyzed.It is found that the oxide film on the original surface of 7075 aluminum alloy can temporarily improve the surface friction reduction during the friction process.When the average laser power is 140 W,the surface wear resistance is the best.Under the condition of 1N friction load and small cleaned surface roughness,the existence of molten layer can improve the friction reduction and wear resistance of cleaned surface.When the friction loads are 5N and 10 N,the surface roughness is the main factor affecting the surface friction reduction of 7075 aluminum alloy.The increase of the roughness caused by the molten layer will reduce the friction reduction and wear resistance of the cleaned surface.(3)The changes of average laser power,galvanometer scanning speed and cleaning times have a great influence on the corrosion behavior and corrosion resistance of 7075 aluminum alloy surface.The removal degree of oxide film is an important factor affecting the corrosion resistance of the cleaned surface.The thermal oxidation in the cleaning process can improve the corrosion resistance of the cleaned surface,but the surface melting phenomenon can reduce the corrosion resistance of the cleaned surface.After laser cleaning,the substrate elements of 7075 aluminum alloy will also participate in the corrosion process.