| Nickel-based superalloys are widely used in aircraft engines,gas turbines and other parts due to its excellent mechanical properties.However,as a typical difficult-to-machine material,the cutting heat generated in the cutting process can easily lead to burns on the surface of the workpiece,tool wear and other phenomenon.Therefore,it is crucial to reduce the cutting temperature of this kind of workpiece during cutting process to improve the processing surface quality.A large amount of cutting fluid are cast externally in traditional cooling method in order to lower the cutting temperature,the extensive use of cutting fluid results in excessive cutting costs,serious environmental pollution and other adverse effects,and MQL(Minimum Quantity Lubrication)combines the advantages of dry cutting and external pouring cutting,the amount of cutting fluid used is greatly reduced,as well as the processing cost and the environment pollution.At the same time,compared with dry cutting,the cooling and lubricating medium is introduced to improve the cooling and lubrication conditions,which is helpful to improve the machining efficiency.MQL system is divided into two kinds of built-in and external,the market penetration rate of built-in system is not high because of its high price,because of the high cutting temperature which produce cutting fluid steam membrane,the cutting fluid produced by the nozzle of the external system is not conducive to the better penetration of the cutting fluid into the cutting area.Therefore,this paper proposes a combination of internal cooling tools and MQL technology,so that the cutting fluid is accurately sprayed on the cutting edge of the tool,the quality of processing surface is improved and the processing concept of green manufacturing is conformed,and it is conducive to the sustainable development of manufacturing.In this paper,through the construction of test platform of internal cooling tool MQL cutting,as well as the theoretical calculation,numerical simulation,processing test,test analysis and other methods,the cutting parameters optimization research of nickel-based superalloy was carried out,the specific research contents were as follows:Firstly,the lubricating and infiltration mechanism of the cutting fluid in the MQL process were analyzed theoretically,and the heat source model of MQL cutting was established to calculate the heat transfer coefficient and the friction coefficient under different cooling modes.Secondly,the finite element model of two-dimensional cutting was established based on AdvanteEdge Fem software,and the influence of different cooling conditions on cutting force,cutting temperature,Mises stress and chip formation process was studied.Then,the turning test of Ni-base superalloy GH4169 with Sialon ceramic inserts based internal cooling tool was used to study the effects of different cooling conditions and cutting parameters on cutting force,cutting temperature,surface roughness,chip morphology and surface morphology of machined workpiece.The empirical prediction model of cutting force was established.Finally,the main factors of cutting on the surface roughness under the condition of MQL through the combination of factor analysis and center composite design(CCD)are selected as follows: cutting speed,feed rate,coolant flow rate and cutting depth,The prediction model of surface roughness is obtained by the four factors and four levels center composite design,as well as the influence law of each influencing factor on it and the optimal range and the optimal parameter combination of the multi-response variable are verified by the verification test,which providing technical support for selecting reasonable cutting parameters and improving processing efficiency. |
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