Mechanism Of CVD Diamond Material Removal By Nanosecond Laser

Diamond material has been widely used in abrasion resistant materials and thermal conductive materials due to its extremely high hardness and excellent thermal conductivity.But the high hardness of the material poses a huge challenge to its formation,especially in precision machining.Traditional processing methods such as grinding is with an extremely low efficiency,and new processing methods such as laser processing can't meet the requirements of finishing quality.Currently,the hybrid processing method is more used,which can improve the processing efficiency and quality.Regarding to the laser processing of CVD diamond,the influencing factors are discussed by combining theoretical analysis with experiment in this paper to realize the controllable laser processing of CVD diamond.Main research contents and conclusions are as follows:(1)Based on Gaussian pulse laser beam,the influence of laser parameters on point etching of CVD diamond was analyzed.Under the irradiation of gaussian pulse,an etching pit with approximate twodimensional gaussian contour will appear on the surface of diamond,and the laser etching pit will become deeper and wider with the increase of laser power and pulse times.The pit size is in the tens of microns and can be used to construct surface structures of micron scale.In addition,the width and depth of laser etched lines on CVD diamond surface under different laser power and scanning speed were studied.It is found that the etched lines obtained by increasing the power and decreasing the speed extend in the depth and width,but the extention mainly works in the propagation direction of the laser beam,i.e.,the depth direction.In addition,the depth of line etching is more sensitive to the variation of laser parameters,and the difference of etching phenomenon caused by power change is more obvious.(2)Based on the trajectory of pulse and Gaussian laser beam,the energy model of processing surface is established.This paper studies the removal depth and surface roughness of CVD diamond when the laser parameters change,and calculates the corresponding mean value and roughness value of the energy model surface at the same time,namely the inhomogeneity of the energy distribution,according to the established model.Single-factor experiments on laser power,scanning speed,filling distance,defocusing and laser beam offset show that material removal depth can be adjusted in the range of 10 ?m ? 90 ?m,while surface roughness can be changed in the range of 1.0 ?m ? 3.5 ?m by adjusting laser parameters.(3)In view of the grain size of CVD diamond,the thermal conductivity of polycrystalline materials was studied,and a new thermal conductivity model was established by modifying the definition of grain boundary concentration of polycrystalline materials.The differences of CVD diamond samples with different grain sizes in laser processing were analyzed,which can be explained well by the relationship between thermal conductivity model and grain size.The results show that the thermal conductivity of fine grain CVD diamond is low,the material removal efficiency is low,but the surface quality is good,while the coarse grain is opposite.The maximum material removal depth in the experiment was obtained when the laser power of sample 3 was 6.8 W,the filling interval was 2 ?m,and the scanning speed was 20mm/s.Sample 1 obtained the seat surface when the filling spacing is 8 ?m,the laser power is 3.6 W,and the scanning speed is 160 mm/s.To sum up,in the laser processing of CVD diamond,the surface processing quality can be improved under the condition of ensuring high processing efficiency.