Research On Tool Damage And Tool Life During High Speed Milling Of Nickel Base Superalloy With TiAlN Coated Tools

With the wide application of difficult-to-cut materials and the development of modern cutting technology towards high-speed and green dry cutting,advanced manufacturing industry has put forward higher requirements for tool cutting performance.Tool coating technology can effectively improve the overall tool cutting performance.Coated cemented carbide tools are widely used in high-speed cutting of materials due to their excellent properties.However,in the high-speed intermittent cutting process of difficult-to-cut materials such as nickel-based superalloys,the interaction between the tool and the workpiece causes the severe plastic deformation in the local area of workpiece,and the intense friction at the tool-workpiece interface.The resulting cutting heat coupled with the serious work hardening leads to rapid tool wear.At the same time,due to the poor toughness of the coating,the mechanical-thermal impact load in the intermittent cutting process leads the tool coating to easily peeling,chipping and other phenomena,accelerating the process of tool failure.Therefore,in this thesis,the tool coating damage form,tool failure mechanism and tool life of TiAlN coated cemented carbide tools in high-speed milling Inconel 718 are studied.Firstly,the physical and mechanical properties and morphology of TiAlN coated cemented carbide tools are analyzed.The composition and structure of the coating are analyzed through EDS analysis,microscopic observation of cross-section morphology,and X-ray diffraction testing.The interface bonding between the coating and the substrate is analyzed,and it is found that there are microcracks,holes and other defects at the coating-substrate interface.The surface roughness,hardness and elastic modulus of the coating are measured.Scratch tests are conducted on coated tools to analyze the interface bonding force between the tool coating and the substrate,as well as the damage and failure forms of the coating during the scratch process.The high-speed milling experiment and finite element simulation of TiAlN coated carbide tool cutting Inconel 718 are carried out.Based on the finite element simulation software Abaqus and the J-C constitutive model,the finite element simulation model is established by applying appropriate damage initiation and damage evolution techniques.The cutting force and chip morphology obtained by the simulation are compared with the high-speed milling test results.The simulation results are in good agreement with the test results,and the accuracy of the finite element simulation model is verified.The influence of cutting speed on the maximum cutting temperature and tool temperature distribution is studied.The tool temperature is mainly distributed on the rake face and increases with the increase of cutting speed.The chip morphology obtained by milling test and cutting simulation is analyzed.It is found that the TiAlN coated tool will form sawtooth chip during high-speed milling of Inconel 718.The influence of cutting speed on macroscopic chip morphology and the degree of sawtooth chip is studied.By comparing the chip morphology and cutting force,it is found that the fluctuation of cutting force corresponds to the sawtooth chip morphology,and the higher the degree of sawtooth chip,the greater the influence on the fluctuation of cutting force.The influence of the formation of sawtooth chip on tool wear is preliminarily analyzed.The generation of sawtooth chip accelerates the tool failure process.The coating damage,tool wear morphology and mechanism,and tool life of TiAlN coated tools in high-speed milling Inconel 718 are systematically studied.Using the finite element simulation software Abaqus,a numerical simulation model is established by combining the extended finite element method and the cohesive element method to simulate the crack initiation and propagation behavior during the cutting process of the coated tool.The effects of cutting distance and cutting speed on coating damage and tool wear are studied.In the process of milling Inconel 718 with TiAlN coated tools,adhesive wear,abrasive wear and diffusion wear occurred.On the rake face and flank face of the coated tool,the coating damage is mainly peeling and wear.With the increase of cutting distance,the tool appears chipping phenomenon.The cutting speed has an important influence on the boundary wear.With the increase of cutting speed,the wear at the boundary ranges from slight wear to cracks penetrating the cutting edge and then to the fracture of the substrate material.According to the results of milling test and cutting simulation,as well as the observation of wear morphology,the influencing factors of tool nose and rake face and flank face coating damage during milling are analyzed.The effect of cutting speed on tool failure and tool life of TiAlN coated tool milling Inconel 718 is studied.With the increase of cutting speed,tool life decreases.Tool breakage caused by impact,mechanical fatigue and thermal fatigue during milling is the main reason affecting tool life.The increase of cutting speed is more likely to cause early tool breakage.