| Ceramic cutting tool material has become one of the ideal materials for cutting tool manufacturing in high-speed cutting and processing field due to its excellent heat resistance,wear resistance and high-temperature strength.At present,many scholars study ceramic cutting tools in blade form.There are relatively few studies on structure design and manufacturing of solid ceramic end milling tool and its cutting performance.At the same time,when high-speed cutting difficult-to-machine materials with carbide milling tool,there are still outstanding problems such as short life and low machining efficiency.Ceramic tools(blade form)have shown good performance in high-efficiency machining of some difficult-to-machine materials.Therefore,in this study,high temperature alloys from typical hard-to-machine materials are selected as cutting objects,aiming at their difficult-to-machine characteristics such as high toughness,low thermal conductivity and high viscosity,and based on the advantages of ceramics in tool material properties,the structure design,manufacturing and cutting performance of high-performance silicon nitride ceramic solid milling tool are studied from the perspective of cutting mechanics.General research ideas in this paper:Firstly,from the angle of tool design and manufacturing,the spatial geometry structure of silicon nitride ceramic end milling tool is designed,modeled and ground.Secondly,from the angle of milling vibration,the chatter stability of the ceramic end milling tool is evaluated and the structure of the milling tool is optimized based on the chatter suppression mechanism.Finally,from the cutting performance point of view,the milling performance of silicon nitride ceramic end milling tool is analyzed and evaluated.In this research,a new type of ceramic milling tool for hightemperature alloy cutting has been developed,which improves the cutting efficiency,the machined surface quality,enriches the existing types of ceramic tools and is beneficial to the development of high-speed cutting technology for difficult-to-machine materials in China.Therefore,it has broad application prospects and practical significance.The research on structure design and manufacturing process of high-performance silicon nitride ceramic monolithic end milling tool was carried out.The structural design criteria of high-performance silicon nitride ceramic monolithic end milling tool are proposed,and the spatial geometry of multi-section circular arc edge and wavy groove is independently designed.The structural parameters of tooth number,tool body length,helical angle,front angle and rear angle are optimized.The high-speed cutting simulation test and the multi-section circular arc radius are carried out by Advantage software.Based on Helitronic Tool Studio tool grinding software,the spatial geometry structure model of high-performance silicon nitride ceramic monolithic milling tool is established,the process route of precision manufacturing is explored,the corresponding grinding process planning and grinding parameters are formulated and closely checked,and four different silicon nitride ceramic monolithic milling tools are successfully manufactured.The silicon nitride ceramic milling tool is a composite ceramic material milling tool based on silicon nitride.Four tools are uniformly named as S1,S2,S3 and S4.The research on milling chatter stability of high-performance silicon nitride ceramic solid end milling tool was carried out.The modal characteristics of silicon nitride ceramic end milling tool system are analyzed by hammering modal experiment.The obtained modal parameters are used to analyze the milling chatter stability,and the chatter stability lobes are plotted to predict the milling chatter stability.The milling stability of the ceramic end milling tool is verified by the change of vibration acceleration signal and the surface chatter morphology of the workpiece.The results show that the milling process of S4 ceramic milling tool is smoother,and has better vibration resistance than the other four milling tools.Moreover,the average spacing of surface vibration of S4 ceramic milling tool is 20%,12%,21%and 23%lower than that of S1～S3 ceramic milling tool and carbide milling tool respectively,which verifies that the milling process of four ceramic milling tools has better stability.Furthermore,based on the chatter suppression mechanism,a structural optimization scheme of high-performance silicon nitride ceramic end milling tool was proposed and the structure of ceramic end milling tool was optimized.The cutting performance of high-performance silicon nitride ceramic monolithic end milling tool for milling nickel-based superalloy was studied.Comparing with the milling performance of commercial cemented carbide milling tool,this paper makes in-depth analysis and evaluation on cutting force,tool life,cutting efficiency and surface roughness of machined surface,explores its wear law,and reveals its failure form and wear mechanism.The results show that S4 ceramic end milling tool has the best wear resistance,and its milling time is 14 times longer than that of cemented carbide milling tool,metal removal rate of material reaches 8.15 cm3/min,and cutting efficiency is 1.5 times higher than that of commercial cemented carbide milling tool.The cutting force of four ceramic milling tools is mostly smaller than that of carbide milling tools.The cutting temperature of the new ceramic milling tool with a sharp cutting edge is reduced by about 96℃ compared with the worn milling tool.Four ceramic milling tools can achieve better surface quality than carbide milling tools.The main wear mechanisms of the rear and front face of four ceramic end milling tools are bond and diffusion wear.The cutting performance of silicon nitride ceramic milling tool was studied under the mixed cutting environment of MQL and MQL with water.It was found that the process condition of mixing MQL and water with oil-water ratio of 1:1 can effectively reduce tool wear,reduce cutting resultant force and obtain better surface quality of workpiece compared with the dry cutting and pure MQL.The cutting performance analysis of the ceramic milling tool with optimized structure shows that the service life of the ceramic milling tool is further extended and the wear value of the flank face is 57.3%lower than that of the ceramic milling tool without optimization.The optimized ceramic milling tool can obtain smaller cutting force and lower cutting temperature,and the surface roughness of the machined workpiece is smaller,and the defects of the machined surface are fewer.The wear mechanism of the optimized ceramic milling tool has little change,but the degree of wear and failure is much lower than that of the unoptimized ceramic milling tool,which verifies the effectiveness of the structural optimization scheme. |
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