| In the development of modern aeronautics industry,superalloy is one of the main material of aeroengine,occupying an irreplaceable position.Nickel-based superalloys have good oxidation resistance,high temperature resistance and corrosion resistance.However,due to the difficult-to-machine characteristics of nickel-based superalloys,there exists intense mechanical and thermal loads near the cutting edge on the rake face of the tool,which leads to the acceleration of tool wear and the decrease of tool durability.Therefore,it is an important way to improve the cutting performance of cutting tool to design reasonable micro-groove structure near the cutting edge on the rake face of the tool.In this paper,the special CNC tool for turning nickel-based superalloy GH4169 is taken as the object of study.The aim of this study is to control cutting energy distribution,reduce cutting temperature and improve tool durability.Based on the shape of temperature field,the design of micro-groove near the cutting edge on the rake face of the tool is carried out,and a new micro-groove cutting tool for turning superalloy GH4169 is designed and manufactured innovatively.Combining theoretical researches,finite element simulations and cutting experiments,the comprehensive cutting performance,cooling mechanism,wear mechanism of the new micro-groove cutting tool are studied.Besides,the chip morphology and its influence are also studied when turning superalloy GH4169 with the new micro-groove cutting tool.Based on the shape of cutting temperature field,the design of micro-groove near the cutting edge on the rake face of the tool is carried out.Taking DEFORM-3D as the cutting simulation platform,the original cutting tool is simulated by finite element method,the data derived from DEFORM post-processing platform is processed and filtered by MATLAB,and the micro-groove surface is constructed in NX 8.5,and the three-dimensional model of the initial micro-groove of the cutting tool is established.In order to make chip easier to flow out and reduce friction between the bottom of chip and the rake face,the influence of rake angle and inner edge of micro-groove on chip formation and flow is studied,and then the initial the shape of micro-groove should be optimized.Through cutting simulation experiments,the influence laws of micro-groove shape on cutting temperature and cutting force are analyzed,and the relevant models are established.Then the main shape sizes of micro-groove are determine.Finally,the shape optimization of micro-groove is finished.Research on basic theory of the cutting process of the new micro-groove cutting tool turning superalloy GH4169.According to the cutting characteristics of nickel-based superalloy,the cutting mechanics model of the new micro-groove cutting tool is established.Based on Oxley-Wilsh cutting theory and cutting experiment,the cutting equation of the micro-groove cutting tool is established for turning superalloy GH4169.Based on the friction characteristics of cutting GH4169 superalloy with the micro-groove cutting tool,the corresponding friction model of tool-chip contact zone is established.Based on the principles of metal cutting and heat transfer,a model for calculating the cutting energy of micro-groove cutting tool is established in oblique cutting process,and the effects of the micro-groove structure on shear and friction energy are studied.By combining cutting test,numerical calculation and theoretical analysis,a comprehensive evaluation method for cutting performance of the micro-groove cutting tool is established.By means of comparative analysis,a reasonable cutting test scheme is designed to analyze and evaluate the comprehensive cutting performances of the new micro-groove cutting tool,in terms of cutting forces,cutting temperature,surface quality of the machined workpiece,tool life,friction and wear characteristics of the tool-chip interface.The variation of cutting energy with cutting parameters is analyzed emphatically.The heat generation and distribution mechanism of cutting energy and its superposition effect upon cutting temperature on the rake face of tool are explored,and the cooling mechanism of the micro-groove cutting tool is further revealed.By testing and analyzing the wear of the rake face and flank face of the new micro-groove cutting tool,it is found that the wear mechanisms of the new micro-groove cutting tool are abrasive wear,adhesive wear and oxidation wear.Based on the processing characteristics of nickel-based superalloy GH4169,the chip deformation and its influence of cutting superalloy GH4169 with the new micro-groove tool are analyzed and studied.The effects of micro-groove structure on chip shape,curling radius,serrated degree of chip,microhardness of shear band and chip edge are studied by cutting experiments.According to the chip deformation and fractal theory,the fractal characteristics of chip deformation are studied.The fractal dimension calculation model of chip deformation is established.Based on this model,the fractal dimension analysis program of chip is compiled in the MATLAB software platform.The influence of micro-groove structure on chip fractal dimension and the relationship between cutting speed and chip fractal dimension are analyzed.At the same time,the effect of chip edge upon groove wear on the flank face and surface quality of machined workpiece at different cutting speeds is studied.Through the above researches,a new micro-groove cutting tool for turning superalloy GH4169 was innovatively designed and manufactured.It is found that the micro-groove cutting tool makes the cutting heat and energy consumption reduces in the cutting process.The cooling mechanism and wear mechanism of the micro-groove cutting tool are explained.The cutting experiment results show that the micro-groove cutting tool has longer tool life,better effect of chip breaking and excellent comprehensive cutting performance.The research results of this study are significant for promoting the progress of processing technology of difficult-to-machine materials and enriching the design method and theory of micro-groove design near the cutting edge on the rake face of tool. |
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