Modeling And Prediction Of Surface Topography Of Nickel-based Superalloy GH4169 In Sequential Milling

GH4169 has excellent properties such as high temperature resistance and thermal fatigue resistance,and is widely used in the aerospace industry.The characteristics of GH4169 such as large cutting force and severe work hardening will cause the surface to be roughened during the machining process and the machined surface topography affects the fatigue performance,friction and wear performance and corrosion resistance of the parts.As a traditional processing method,milling can realize the processing of various planes,cavities,steps,grooves and other characteristic structures.Therefore,the study of the surface topography formation mechanism and surface topography simulation of GH4169 in the sequential milling process can optimizing the production process of GH4169.This paper studied sequential milling process of GH4169,took the milled surface topography as the research object,and took the initial surface topography and the work-hardened layer as the research factors.Through theoretical modeling,experimental research,model simulation and mathematical statistical analysis,the change law of milling force and surface topography in the current step of milling process with the initial surface topography and work-hardened layer was analyzed.The influence mechanism of the initial surface topography and the work-hardened layer on the milled surface topography was revealed.The formation mechanism of the surface topography in the sequential milling process was explored,and the mapping relationship between the processing parameters and the surface roughness of the sequential milling process was explained.Firstly,based on the degree of work hardening,a milling layered model was proposed to layer the workpiece material.Considering the influence of the initial topography of the machined surface,the instantaneous cutting thickness model was modified,and a milling force model with variable cutting force coefficients for sequential milling process was established.Simulation verification of milling force showed that the rough initial surface topography and work-hardened layer will increase the difficulty of milling,thereby increasing the milling force.The established milling force prediction model can effectively predict the change law and value of milling force in the process of sequential milling.Secondly,based on the kinematics and dynamics principles of the milling process,the effects of the initial topography of the machined surface and work-hardened layer were equivalent to the effect of tool vibration,and the actual trajectory equation of the cutting edge was established.Using the Z-MAP algorithm,a three-dimensional surface topography prediction model for the sequential milling process was established,and the relative error of the prediction of the model was less than 20%.The two-step sequential milling verification experiment explained the positive correlation law of the initial surface topography on the surface topography and the influence mechanism of the microhardness gradient change on the surface topography.Finally,according to the initial work hardening state of the workpiece surface,an experimental group and a control group were established for orthogonal milling experiments.Through statistical analysis,the influence law of cutting parameters in sequential milling under different work hardening degrees was explained.The surface roughness prediction model under different initial work hardening states of the surface was established.The experimental results showed that in addition to the radial cutting depth as a common significant factor,the significant factors in the control group and the experimental group were feed rate and cutting speed,respectively.The established surface roughness model considering the different initial work hardening states of the surface were in good agreement with the actual situation,and can realize the accurate prediction of the surface roughness of GH4169 during the sequential milling.