Research On Atmospheric Plasma Polishing Technology Based On Arc Discharge

Damage layer removal is the most critical step in ultra-smooth surface processing.The existing damage layer removal technology is not efficient and unstable.Atmospheric plasma polishing technology can achieve atomic-scale chemical removal of the material surface.The surface roughness is extremely low,which can be ignored,and it has the ability to remove the damaged layer with high efficiency,but it cannot suppress the temperature effect,resulting in the inability to achieve deterministic removal.Atmospheric plasma polishing by arc discharge has great potential in suppressing the temperature effect,In this paper,the temperature effect and efficiency of arc discharge atmospheric plasma polishing technology in the removal of damage layer of fused silica optical elements are studied.The main research contents are:1)The different working modes of arc discharge atmospheric plasma are studied.The arc discharge atmospheric plasma can be divided into two working modes according to the carrier gas pressure.The two working modes are:the fire polishing mode when the carrier gas pressure is 0.02～0.035 MPa and the reaction mode when fluorine-containing gas is introduced when the carrier gas pressure is 0.035～0.07MPa.2)The temperature characteristics of atmospheric plasma fire polishing are studied by simulation.The simulation results show that in the power range of 130W～250W,the fused silica surface is in the melting temperature range of 1986K～2503K,and the surface ablation polishing can be achieved.When the power is above 250W,the fused silica is vaporized and removed;and the temperature and thermal stress have a negative correlation with the nozzle diameter;the temperature and the discharge power have a positive correlation.3)The method of process test is used to study atmospheric plasma chemical reaction polishing.The removal rate and processing stability of atmospheric plasma chemical reaction under different parameters were studied.The experimental results show that a higher removal rate can be obtained by introducing reaction gas from the back end.It is found that the removal rate increases with the increase of the discharge power.When the discharge power is 871W,N2 gas pressure is 0.05MPa,SF6 gas flow is 10SLM,and the working distance is 2mm,the removal rate can reach 28.35mm3/min.4)The material test analysis method is used to study the surface secondary adsorption.The test results show that the secondary adsorbate is mainly fluorocarbon;and as the surface secondary adsorbate increases,the hardness of the component’s decreases;the presence of secondary adsorbate reduces the light transmittance of the element by 31.14%;the surface secondary adsorbate are removed by the small grinding head polishing method and the initial transmittance can be restored,and the mechanical properties close to the material matrix.Based on the above research results,the arc-discharge atmospheric plasma polishing technology can achieve high-efficiency removal of the damaged layer of fused silica optical components by fire polishing melting and chemical reactions polishing.Provide process and data support for the arc discharge atmospheric plasma polishing technology to remove the damaged layer.It is helpful to realize the application of arc discharge atmospheric plasma polishing technology in the process of removing damage layer in ultra-smooth surface processing.