Ultrashort Pulse Laser Ablation Mechanism And Experimental Study Of Iron-based Metal Materials

In recent years,with the continuous enlargement of the size of solid-state laser drivers,the laser flux in laser devices has been continuously improved.At present,the internal cleanliness of high-power laser devices has become one of the problems restricting the development of laser inertial confinement nuclear fusion.The internal environment of the optical transmission channel deteriorates sharply after loading the laser during the operation of the Shenguang-III device,optical components will be damaged by laser when a large amount of particulate contaminants deposit on the surface of the optical components.It is discovered that part of particulate contaminants are generated when the stray light irradiates the wall of the metal tube,then the metal particles will be adsorbed on the surface of the optical components.Therefore,it is very important to study the damage behavior of laser induced stainless steel components from the source of contaminants.The research can provide theoretical basis for improving the internal cleanliness of high-power laser devices.In this paper,the molecular dynamics method is used to simulate the adsorption process of contaminants on the single crystal iron surface.We study the instantaneous system conformation,the distribution status of contaminants and the system adsorption energy during the adsorption process.The result indicates that contaminants exhibit different adsorption states on the surfaces of different microstructures.The model of laser ablation contaminated single crystal iron is based on the steady-state model of contaminants adsorbed on the single crystal iron surface.Secondly,the ablation processes at Fe surfaces under laser irradiation is investigated with molecular dynamics(MD)simulation combined with two temperature models.The laser ablation process is analyzed according to the distribution of iron atoms at different times,and the pressure inside single crystal iron is analyzed.The ablation threshold of single crystal iron is determined by the state of surface atoms under different laser energy,and this value is compared with the laser ablation threshold of contaminated single crystal iron.Thirdly,laser ablating single crystal iron adsorbed contaminants is investigated with molecular dynamics simulation,and the damage of single crystal iron induced by contaminants under laser Irradiation is researched.The depth of single crystal iron influenced by laser is studied,and time of laser Irradiation will influenced the ablation depth.The results show that the instantaneous loading of energy has a greater effect on single crystal iron materials,and single crystal iron is more easily ablated by the laser when the surface is adsorbed by contaminants.Finally,the experiment of detecting the contaminants in the surface of stainless steel is carried.Droplet contact angle experiment is carried for qualitative analysis of the content of contaminants on the work-piece surface and XPS experiment is used to quantitatively detect the elemental components of the surface contamination.Stainless steel work-piece is ablated by Thales SAGA solid pulsed laser and the damage of stainless steel under different pulse numbers and different laser energy is observed.The macro-morphology of stainless steel after laser ablating is observed by using an Optical Microscope,and the depth influenced by laser under different conditions is analyzed.The micro-morphology of stainless steel under laser irradiation is observed by using scanning electron microscope and three-dimensional profiler.