Research On High Efficient Fixed Abrasive Lapping Of Sintered SiC

Silicon carbide is one of the preferred materials for space mirrors due to its excellent mechanical,chemical,thermal and optical properties,especially for aerospace industry,military industry and other high technology industries,which require extremely high quality of production of SiC and its surface with high quality in nanoscale.Therefore,high efficiency,high precision and low damage are required for processing silicon carbide.The advantage of hydrophilic fixed abrasive pad(FAP)was used for optimizing the production process of the reaction-sintered silicon carbide in this project,in order to solve the problem of poor wear resistance and insufficient FAP self-conditioning ability when lapping the silicon carbide.By making the of processing routes of SiC workpiece with mortar-assisted aggregate FAP and obtaining the optimal process parameters,which provided reference and guidance for FAP lapping silicon carbide mirror,results were found:(1)The effects of FAP hardness,mortar particle size and concentration and primary particle size of aggregate diamond on lapping silicon carbide were explored by single factor experiment.The experiment found that material removal rate(MRR)is higher if the FAP is harder and particles are more concentrated with larger size.However,the surface roughness was not sensitive for these parameters.In addition,the lapping performance of the aggregate diamond FAP was better than the single crystal diamond FAP.The larger the diameter,the higher the MRR and the little change in surface roughness.(2)The hardness of FAP was increased by adding copper powder,meanwhile improved the selfconditioning ability of FAP and the lapping effect by reacting with the triethanolamine.By using orthogonal experiment technique,it is found that loads,primary particle diameter and lapping speed had significant effect on the lapping performance.The best lapping performance was obtained by using aggregate diamond FAP with mortar concentration of 3wt%,pressure of 21 kPa,grinding disc/workpiece speed of 65/60 r/min and primary particle size of 5-10 um.The average MRR was 3.354 um/min,and the surface roughness Ra was 82.06 nm.(3)The mechanism for efficient fabrication of aggregate diamond FAP was analyzed by establishing MRR model.The MRR model for FAP grinding of silicon carbide was obtained by analyzing the mechanical relationship among workpiece,abrasive particle and FAP,which were obtained by establishing the mechanical theory model.The correction coefficient is introduced for explaining he mechanism of FAP efficient processing of aggregate diamond more precisely.It was found that the MRR increased with the increase of mortar particle size,concentration,lapping speed,loads and primary particle size.Moreover,it was found that aggregate diamond has good self-sharpening,and mortar was conducive to the improvement of FAP self-conditioning ability and better processing effect.