Research On Cutting Characteristics And Lubrication-Cooling Mechanism Of Ni-based Superalloy GH4169 Under High Pressure Cooling

With the rapid development of aviation manufacturing industry,the application of superalloy is growing,which is mainly due to its good wear resistance and excellent microstructure,etc.In the working conditions of high temperature and high pressure,it can not only keep high tensile strength and yield strength,but also have lower creep property,higher corrosion resistance and oxidation resistance.However,due to its characteristics of superalloy materials,it is easy to cause problems such as high cutting force,high cutting temperature and serious tool wear,etc,which is because of the high microstructure strengthening phase hardness,the high shear stress,and the low thermal conductivity in the process of cutting.So the superalloy is one of the difficult-to-cut materials.With the development of auxiliary cutting equipment,the emergence of high pressure cooling cutting technology provides technical support for solving the difficult machinability of superalloys.Therefore,in order to improve the cutting technology of superalloy,the cutting characteristics of Ni-based superalloy GH4169 under high pressure cooling is studied in this paper,taking the nickel-base superalloy GH4169 as the research object and the application of high pressure cooling as the research background.It is of great significance for improving the level of China's high-end equipment manufacturing industry,especially the production of superalloy parts.In order to reveal the influence of high pressure coolant on cutting deformation zone,the jet characteristics of high pressure coolant are analyzed theoretically based on the theory of fluid mechanics,and then the theoretical impact force and action area of high pressure coolant are obtained.On this basis,the mechanism of cooling and lubrication of high pressure coolant are studied.According to the stress distribution of contact area between tool and chip,the theoretical models of contact length between tool and chip,lubrication and cooling effect under high pressure cooling are established respectively,which provides theoretical basis for subsequent analysis of cutting characteristics of high pressure cooling.Aiming at the problems of large cutting force and poor surface quality in the process of cutting superalloy,the cutting mechanism of high pressure coolant is revealed by taking the cutting force,surface roughness and residual stress for the cutting of high pressure coolant as the research objects and combining with the cooling and lubrication mechanism of high pressure coolant.The characteristic changes of cutting force and machined surface quality(surface roughness and residual stress)in the process of cutting under high pressure cooling are obtained by theoretical analysis.On this basis,the influence of high pressure cooling process parameters(different coolant pressures),cutting parameters,and cutter geometry parameters on the above characteristics are obtained by combining with the experiment of high pressure cooling.The prediction model of machined surface roughness of cutting GH4169 by PCBN(Polycrystalline Cubic Boron Nitride)under high pressure cooling is established,which provides theoretical basis for optimizing cutting parameters.Aiming at the problem of the chip is not easy to break in the process of cutting superalloy,the influence of high pressure coolant on cutting deformation is further analyzed from the perspective of chip breakage by combining with the injection characteristics of high pressure coolant.The variation rules of the macroscopic and microscopic morphology of the chip under different coolant pressures,cutting parameters and cutter geometry parameters are revealed by the experimental study of cutting under high pressure cooling.On this basis,the formation mechanism of serrated chip in cutting superalloy GH4169 under high pressure cooling is revealed by he adiabatic shear theory.The influence of high pressure coolant on chip curl radius is analyzed by force analysis of cutting deformation zone and combining with the impact force of high pressure coolant.Finally,the theoretical model of chip curling and breaking under high pressure cooling is established to provide theoretical support for chip control.Aiming at the problem of tool wear in the process of cutting superalloy,the wear mechanism of PCBN tool is revealed by the cutting test of high pressure cooling.The main wear patterns of PCBN tool under high pressure cooling are determined by comparing with the normal pressure cooling.On this basis,the effects of different cooling conditions,cutting parameters and geometric parameters on tool life are further analyzed.The prediction model of tool life of PCBN in cutting GH4169 under high pressure cooling is established by the adaptive genetic algorithm,which provides a theoretical basis for the optimization of cutting parameters.Finally,the cutting parameters,tool geometric parameters and coolant injection angle of cutting Ni-based superalloy GH4169 by PCBN under high pressure cooling are optimized by the above research contents,genetic algorithm and matrix analysis method.The above research results can provide theoretical basis and technical support for the popularization of high pressure cooling cutting technology and the machining of superalloys with high efficiency and high quality.