Study On Surface Integrity For Machining Superalloy With High-pressure Coolant By PCBN Tools

The needs of aero-engine,nuclear reactor and other core equipments have prompted the development of superalloys.Superalloy is one of the multi-element metal,which is still in the environment of more than 600? to maintain the stability of the organization with high fatigue resistance,corrosion resistance and oxidation resistance,the material properties of the superalloy itself make it plastically deformed during procesed,resulting in surface quality problems such as work hardening,large residual stress and the like.In view of the above phenomenon,this paper designs to cut the nickel-base superalloy using PCBN tool under high-pressure cooling and through the test,theoretical analysis and simulation verification we can study the surface roughness,work hardening,residual stress and other phenomena to reveal the superalloy workpiece surface integrity after processing,this has many reference values,for example,effectively improving the utilization of superalloys and PCBN tool life.First,the single factor and orthogonal test are designed and implemented under high-pressure coolant,and PCBN cutting tools are used to cut the superalloy GH4169,then cutting force is of measurement and acquisition in the cutting process,which aims to explore the law of cutting force and model building,this will facilitate the follow-up study,such as the effect of cutting force on the work hardening,surface roughness and other indicators,finally the processed-surface defects are observed and analyzed to discuss the effect of surface defects on the surface quality under high pressure coolant.Second,compared with conventional coolant,and based on the formation of the machined surface,through the theoretical analysis of surface roughness and the influence of coolant pressure and cutting parameters on the surface roughness,the passage clarify the rule of surface roughness when cutting superalloy under high pressure coolant.Based on the response surface method,the surface roughness model of high pressure coolant is established,then the model is verified with the test.Third,the factors affecting the work hardening and the evaluation methods are analyzed,also the causes and influential factors of the work hardening under the high pressure coolant are discussed.From the perspective of cutting force the depth model of the hardened layer under high pressure coolant is established,and the influence of cutting parameters on the work hardening rate and microhardness is analyzed.Residual stress is of great significance to the processing technology of superalloy,from the study of residual stress mechanism in conventional cutting,the text extends to the rule of residual stress under high-pressure coolant.the rule of surface residual stress distribution of superalloy under high-pressure coolant is clarified combined with finite element simulation.Finally,for the white layer of superalloy under high-pressure coolant,the microstructure of cutting superalloy was analyzed by using the depth of field microscope and scanning electron microscope to investigate the characteristics of white layer and microstructure.White layer forms on the surface of the workpiece and white layer thickness have a significant impact on the surface quality and use performance.Therefore,the effect of coolant pressure and cutting parameters on the thickness of white layer is quantitatively studied,and the effect of cutting parameters and cutting force on the thickness of white layer is also discussed.