Research On Polishing Technology Of CVD Diamond Coating Based On Femtosecond Laser

CVD diamond coating has high hardness,high thermal conductivity,good insulation and high temperature resistance.Therefore,it is widely deposited on various tool surfaces to enhance the surface hardness,wear resistance and service life of the tool.However,the deposited diamond coating has a high surface roughness,which seriously restricts the application in the field of precision.Therefore,obtaining a low roughness surface is an urgent problem to be solved.Although the traditional laser polishing technology has achieved some results in practical applications,it has the disadvantages of high cost and low efficiency,and is not suitable for polishing diamond coatings.Because femtosecond laser has the advantages of short pulse width,high peak power,and small heat affected zone,this topic uses superprecision polishing of CVD diamond coating by femtosecond laser.The main research contents are as follows:(1)The current status of CVD diamond coating polishing is summarized.Combining with domestic and foreign literatures,the problems and shortcomings of traditional polishing of CVD diamonds are summarized.In this regard,a new method of femtosecond laser polishing is proposed,and the research progress of femtosecond laser processing superhard materials is described.(2)The energy coupling and interaction mechanism of femtosecond laser and CVD diamond coating were studied.The mathematical model of femtosecond laser heat source generation and heat source energy distribution is analyzed,and the formation mechanism of multiphoton ionization,avalanche ionization,phase explosion,Coulomb explosion and periodic stripe structure generated during the coupling of materials and femtosecond laser energy is carried out.Systematic explanation shows the essence of ablation removal of CVD diamond coating under the action of femtosecond laser.(3)An experimental study on femtosecond laser polishing of CVD diamond coatings was carried out.The effects of different femtosecond laser processing parameters(laser power,repetition frequency,scanning speed)on the processing results were analyzed.The results show that femtosecond laser power and scanning speed have great surface roughness,surface topography and material removal rate.Effect;repetition frequency has little effect on processing results.Through multiple sets of tests,it is concluded that when the femtosecond laser power is 100 mW and the scanning speed is 1.6mm/s,the roughness of the polished CVD diamond coating surface is about 0.149?m.The white light interferometer,scanning electron microscope and Raman spectrum are used.The diamond coating was characterized and found.The results show that the femtosecond laser polishing area not only has a significantly lower roughness,but also has a denser surface and no serious degree of graphitization,which basically meets the requirements of low friction surface of CVD diamond coating.A mathematical model was established based on the shape of the ablation incision.The maximum removal rate of the CVD diamond coating at different powers was obtained by numerical fitting method,which improved the utilization of laser energy.