Research On Laser-induced Cavitation Characteristics And Cavitation Corrosion Mechanism Of 6061 Aluminum Alloy In Sandy Water Environments

The bottom shell plating,side shell plating and pipeline of marine vessels are exposed to various water environments throughout the year.The waters are rich in solid particles,which may promote the occurrence of cavitation and accelerate the erosion process of marine alloys.In this work,laser technology was used to investigate the impact of particle size on cavitation behaviors in the suspension environment.In this paper,based on the laser-induced cavitation device,sandy water environments are simulated by water-based suspension containing particles.combined with high-speed photography and hydrophone technology,the bubble pulsation characteristics in different aqueous environments are experimentally studied.The6061 aluminum alloy is used as the solid boundary to investigate the effect of particle size on surface cavitation erosion.The cavitation erosion mechanism of particle size on marine Al alloys in different environments was clarified.The following are the main contents and results:(1)The dynamics of laser-induced cavitation bubble is analyzed theoretically.The pulsation characteristics of cavitation bubbles are explored from three perspectives:formation theory,dynamics and influencing factors.In addition,the bubble collapse effect and cavitation erosion mechanism near the metal solid boundary have been analyzed to provide a theoretical basis for the subsequent exploration of the pulsation characteristics of cavitation bubble and the cavitation mechanism of marine Al alloys in different aqueous environments.(2)Based on the laser-induced cavitation experiment platform,the high-speed camera and hydrophone are employed to monitor the bubble pulsation behaviors and shock waves,separately.The effects of particle size on cavitation bubble in the infinite domain and near the metal boundary are studied.The number of bubbles,the diameter of bubble,the cycle of bubble,and the shock waves are analyzed in different aqueous environments.The results show that solid particles in the infinite domain increase the number of cavitation bubbles.The number of cavitation bubbles is simultaneously related to the laser energy and the particle size.Under the same laser energy,the maximum diameter of the cavitation bubble,the pulsation period,and two shock waves reach the peak when the particle size is 60 mesh.As the particle size decreases,the shock wave value will show a downward trend due to the reduction of laser energy by smaller solid particles.(3)The effects of cavitation bubble on the surface of marine 6061 aluminum alloy in different aqueous environments are analyzed.The results of cavitation erosion are studied through the surface morphology,roughness and residual stress.The results show that the reduction of the solid particle size in the aqueous environments increases the surface roughness of the Al alloy and the plastic deformation of the surface,thereby aggravating the cavitation corrosion on the surface of the Al alloy.In addition,based on the characteristics of bubble pulsation in different aqueous environments,models of laser-induced cavitation behavior and cavitation erosion are established,and the effect of particle size on cavitation impact and cavitation erosion mechanism on Al alloys are revealed.(4)Electrochemical experiments are conducted to test the electrochemical corrosion performance of specimens after cavitation corrosion in different suspensions.The performance of Al alloys after cavitation corrosion in different suspensions is studied.Compared with deionized water,the passive film on the surface is prone to activation after 6061 aluminum alloy is cavitation-etched in suspension,which will weaken the corrosion resistance of Al alloys.The smaller the particle size contained in the suspension,the higher the degree of weakening of corrosion resistance.