Cryogenic Cutting Mechanism Of Superalloy And Tool Life Extension Mechanism

Iron-based and cobalt-based superalloys have excellent medium-temperature and high-temperature properties,respectively.They are widely used in many fields such as hot-end components of aero-engines,industry,gas turbines of ships,nuclear power,and automobiles.However,in the traditional cutting process,there are many problems,such as large amount of sewage,large cutting force,high cutting temperature,easy wear and low life of the tool,and difficult to guarantee the processing quality and efficiency.With the continuous strengthening of the concept of green manufacturing in the field of cutting,cryogenic cutting technology has been widely concerned.In this paper,aiming at the problem of poor machinability of iron-based superalloy GH2132 and cobalt-based superalloy GH605,the cryogenic cutting mechanism and tool life extension of superalloy are studied by using coated tools,so as to realize green environmental protection,high efficiency and high quality cutting.In this paper,two typical superalloys are deep-cooled by cryogenic treatment.The influence law of different deep cooling temperatures on their microstructure and mechanical properties is studied.To reveal the mechanism of the influence of the cryogenic characteristics of the liquid nitrogen deep cooling treated superalloys on the cutting process.To evaluate and analyze the effects of different injection temperatures of liquid nitrogen on the cutting performance and machined surface integrity of the tools by using Al Ti N coated tools for cryogenic milling tests.By exploring the cryogenic cutting process of superalloys,the optimization of cooling system parameters and tool surface treatment,the goal of delaying tool life is achieved.Firstly,the effects of cryogenic treatment temperature on microstructure,vickers hardness,residual stress,yield strength and tensile strength of GH2132 and GH605 are studied.The results show that with the decrease of cryogenic treatment temperature,the microstructure of the alloy can be optimized,the surface vickers hardness of the alloy can be increased,and the yield strength and durability of the alloy can be improved.Secondly,the influence mechanism of superalloys treated at different cryogenic temperatures in cutting is studied.The effects of milling at different initial temperatures on cutting force,cutting temperature,tool wear mechanism and machined surface integrity are explored.The results show that the initial temperature decreases,the wear width of the flank face of the milling GH2132 tool is not much different,and the main wear mechanism of the tool is abrasive wear and adhesive wear.The main wear forms of the flank face of the milling GH605 tool are coating peeling,bonding,cracks and scratches.The residual tensile stress of the machined surface gradually changes to the residual compressive stress.Thirdly,liquid nitrogen cryogenic jet milling GH2132 and GH605 experiments are carried out to study the effects of different jet temperatures on chip deformation,cutting force,coating tool wear mechanism,tool life and machined surface integrity.The results show that with the decrease of liquid nitrogen injection temperature,the serration degree of chips is aggravated,and the adhesive wear and oxidation wear of the tool are effectively reduced.A relatively high tool life can be obtained when the injection temperature is in the range of-150℃～-190℃,and a smaller surface roughness can be obtained between-30℃～-150℃.Lowering the injection temperature can increase the residual compressive stress on the machined surface.Greatly reduce the plastic deformation of the machined surface.Finally,by optimizing the cryogenic cutting process parameters and cooling system parameters of superalloys and adopting corresponding surface treatment of coated tools,the life extension of cryogenic cutting tools is further realized.The results show that the influence of milling speed v_c and feed per tooth f_zon tool life is significantly greater than that of radial cutting depth a_e.The tool life is the highest when the cryogenic cutting nozzle angle is 45°.Whether it is dry cutting or liquid nitrogen cryogenic jet cutting,the tool life after cryogenic+micro-blasting treatment is improved.