Research On The Cutting Mechanism Of High Temperature Alloy Inconel 718 And Its Innovative And Optimized Tool Desig

Nickel-based superalloys are widely used in the aerospace industry because of their excellent mechanical properties and corrosion resistance at high temperatures.Its poor thermal conductivity and severe work hardening lead to poor machinability,which is a typical difficult-to-machine material.Based on this,to address the problems of low tool life and poor surface quality in machining superalloys,the cutting machinability of the Inconel718 alloy is studied.Starting from the cutting mechanism of Inconel 718 alloy under typical heat treatment process,through the analysis of machining mechanism and cutting theory,microstructure characterization,combination of simulation and experiments,this thesis mainly focuses on the analysis of tool wear by microstructure of workpiece material,reverse identification of material cutting constitutive parameters,modeling and simulation of turning process,and innovative optimization design of rake face structure.The research results would be used as reference for improving the cutting performance of Inconel 718 alloy,optimizing tool structure and cutting parameters.Firstly,the heat treatment test of Incoenl 718 alloy is carried out.The influence of heat treatment process on microstructure is investigated by means of optical microscope,scanning electron microscope,XRD and EDS,so as to reveal the influence mechanism of precipitate phase and grain size on its mechanical properties.The machining mechanism of workpiece material under typical heat treatment process is further explored,and the effect of microstructure-induced thermo-mechanical loads difference on surface morphology,work hardening and microstructure evolution is elucidated by combining cutting force and machined surface/subsurface characteristics.The comprehensive influence of microstructure on tool wear behavior is revealed by analyzing the tool wear mechanism.The results show that heat treatment can significantly change the hardness of the alloy,but the difference in cutting force is small.The deformation behavior of the machined surface is affected by the grain size and the number of strengthened phases.In addition,there are also large differences in tool wear behavior,with solution heat treatment having the best machinability.Secondly,considering the influence of the edge radius on the ploughing force,the Waldorf slip line field is used to modify the cutting force distribution method.Based on this,a mechanism model describing the deformation characteristics of the main shear zone is established,which reveals the variation law of shear angle.A method of identification of cutting constitutive parameters based on physical model is proposed.Taking the data of orthogonal cutting experiment and quasi-static compression experiment as input,the identification of constitutive parameters is regarded as optimization problem,and the error between equivalent stress experiment value and predicted value is taken as objective function to optimize constitutive parameters.The effectiveness of the method is verified by comparing the simulated cutting force and chip morphology with the experimental results.Thirdly,the mathematical model of geometric parameters of local cutting edge under macro tool is established to reveal the influence of tool parameters on local cutting variables.The discrete cutting edge is regarded as a series of oblique cutting elements.Considering the size effect and edge effect,the thermodynamic control equation of chip formation of a single cutting edge is established.Combined with the interaction between chip elements,the chip flow direction and cutting force is numerically solved.The influence of tool parameters on the global chip flow direction is discussed,and the distribution of local parameters(chip flow direction,normal rake angle,edge inclination angle,cutting force and shear strain,etc)along the cutting edge is analyzed.The effectiveness is verified by experimental cutting force.The results shows that the chip flow direction can be controlled according to the appropriate edge inclination angle,main deflection angle,nose radius and cutting speed.In addition,the local geometric parameters and cutting force distribution on the cutting edge can be used to optimize the edge shape.Finally,based on the analysis of the shape of the tool-chip contact area,the cutting edge is miniaturized,and the local cutting parameters at any position of the cutting edge are obtained.Combined with the segmented design concept,the parametric modeling of the twodimensional cutting edge shape is realized.Based on Python data-driven Abaqus simulation model,the normalized optimization functions of cutting force and cutting temperature under different feed rates are established,and the rake face shape and edge radius are optimized.The optimized tool model is obtained by combining all the optimized edge shape with geometric relations,and the tool entity is prepared by powder metallurgy.The experimental results of cutting performance show that the optimized tool reduces the cutting force,cutting temperature and the plastic flow of workpiece material,thus improving the thermalmechanical loads distribution on the cutting edge.Tool-chip contact area reduction makes the smooth outflow of chips,also greatly reduce friction force and friction heat on rake face,so that the tool life is about doubled.In addition,the flank wear bland more uniform,and the adhesive wear and oxidation wear are reduced to a certain extent.