Study On Machining Mechanism And Related Technology Of Nickel Base Superalloy GH4169

Nickel-base superalloy GH4169 has good thermal strength,thermal stability and thermal fatigue properties,it is widely used in aviation,aerospace,marine and chemical industries.The rotor components of engines such as compressor disc,spool,turbine disc,compressor blade and power drive shaft are usually made of this alloy.GH4169 is a typical difficult to machine material,which is mainly characterized by large cutting force,high cutting temperature,severe tool wear,work hardening,serious tool sticking,and difficult chip removal.These factors restrict GH4169 from obtaining good surface quality and high machining efficiency.Therefore,the study of GH4169 machining mechanism is of great significance to improve its machining quality and application range.According to the microstructure of GH4169,the deformation and fracture mechanism of matrix phase and strengthening phase of nickel base superalloy GH4169 were studied from the microscopic field.It is found that the matrix phase is mainly plastic deformation while the strengthening phase is mainly elastic deformation when cutting GH4169,and the strengthening phase is the main source of fracture.Through the dislocation density evolution mechanism,the stress-strain relationship during cutting GH4169 was studied;A constitutive model considering the effects of strain rate,dislocation density,strain gradient,steady-state stress,cutting temperature and other parameters was established.The average relative error of the model was 4.26%.The crack tip morphology and fracture mechanism of the strengthened phase were studied by small-scale yield theory,and the effect of matrix phase slip on the fracture of the strengthened phase was studied;By introducing the phase field variable and establishing the energy functional,the interaction between the two phases in the cutting process is studied.Finally,the formation process of serrated chip during cutting GH4169 is obtained,and the formation mechanism of serrated chip is explained from the microscopic field.Through the tool wear experiment,the main wear morphology and failure mode of cutting tool were studied;According to the micro deformation and micro sliding of the adhesive at the tool chip interface when the chip impacts the tool,the stick slip erosion wear mechanism is proposed.During cutting,the micro convex body on the chip surface adheres to the tool surface and micro plastic deformation occurs.The stick slip movement of the chip along the tool surface produces liquid like erosion on the tool.The stick slip erosion wear of the chip is the main wear form of the cemented carbide tool in cutting nickel-base superalloy.The chip impact tool produces two adiabatic zones at the tool tip,and the adiabatic impact zone I is easy to produce cracks,causing the tool to be damaged,leaving flakes and pits on the tool surface.The adiabatic shear band II causes the chips to be serrated,forming serrated chips.By studying the main wear morphology and mechanism of chip stick slip erosion tool,it is considered that the lip is a typical morphological feature of stick slip erosion,but the number is very small;The pits formed by the impact shear fracture of the lip by the micro convex body and the lamellae produced by the fracture of the cell boundary crack in the adiabatic impact zone are the main morphology after erosion wear.The influence of cutting parameters on surface roughness was studied by single factor cutting experiment,and the main factors affecting surface roughness were determined.The experiment showed that the thermal strength and hardness characteristics of GH4169 had a very important impact on the machined surface quality,and work hardening would aggravate tool wear and lead to the increase of surface roughness.A multivariate Gaussian process regression model for predicting surface roughness is established by using Gaussian process regression method,which takes cutting speed,cutting depth,feed rate and tool rake as input variables and surface roughness as output variables.The model has good portability and replicability through universal description.The maximum relative error and average relative error of the prediction model are 2.7% and 1.5%,respectively.The Zygo interferometer is used to scan the cutting workpiece surface,and the absolute height of 20×40=800 sampling points and reference plane is obtained.The mean and variance of surface roughness are calculated.A multivariate kernel function modeling method with independent adjustable proportional superparameters is proposed.The influence of process parameters on surface roughness is characterized by proportional superparameters.The influence law of the proportional superparameter on the process parameters is obtained: the smaller the proportional superparameter,the greater the influence of the corresponding process parameters on the surface roughness.Through the proportional superparameter,the influence degree of process parameters on surface roughness from large to small was determined as follows: feed rate,cutting depth,cutting speed,tool front Angle,and the above conclusion was verified by experimental study.