| Superalloys have been widely applied in aerospace area due to their excellent mechanical properties under high temperature.However,machining of them has long been viewed as considerably challenging work because they belong to difficult-to-cut material.Iron-based superalloys have superior performance at temperature below 750?and can partially replace more expensive nickel-based superalloys.However,research on their cutting is insufficient,and guidance on their actual machining is limited.In this study,cutting performance of various tools in machining of the iron-based superalloy GH2132 was systematically studied,and the material constitutive model of GH2132 under high temperature and high strain rate was built.It provides reference for the selection of cutting parameters,tools and emulational material parameters of cutting GH2132.By orthogonal cutting tests,empirical formulas of cutting force,cutting temperature,surface roughness and tool life were built for(Ti,Al)N+Ti N coated carbide tools when dry cutting GH2132,and the influence regularity of cutting parameters on them was obtained.In order to improve the machining efficiency of GH2132,from the aspect of controlling the cutting force,it was more favorable to increase the cutting speed than to increase the depth of cut and feed rate.From the aspect of controlling the cutting temperature,it was more favorable to increase the depth of cut and feed rate than to increase the cutting speed.The cutting speed of about50 m/min and smaller feed rate were suggested to ensure quality of the machined surface of GH2132.By single factor cutting tests of cutting speed,performance of various carbide tools and polycrystalline cubic boron nitride(PCBN)tools on cutting GH2132 was studied.Cutting force of carbide tools increases with increase of cutting speed,while that of PCBN tools increases first and then decreases.Adhesion was occurred on both carbide tools and PCBN tools due to superior plasticity of GH2132,and as the cutting speed increases,the degree of adhesion showed a trend to increase.Both tools can obtain high surface quality in dry cutting GH2132.However,when the wear value of the flank faces reached about 0.25 mm,the surface roughness began to increase obviously.(Ti,Al)N+Ti N coated carbide tools showed lower cutting force and longer life than uncoated carbide tools.However,serious adhesion was occurred on their flank faces at the cutting speed of 100 m/min.Therefore,they are not suitable for high-speed finishing of GH2132.The PCBN tools with ceramic bond and low CBN content(?65%)were broken in the early stage of cutting and not suitable for cutting GH2132;the PCBN tools with Co-W-Al ceramic bond and high CBN content(85%)performed well in the cutting process.In order to ensure the surface quality,the suggested cutting time for continuous dry cutting of GH2132 using this types of PCBN tools at different cutting speeds was obtained.By quasi-static compression tests and split hopkinson pressure bar tests,the mechanical behavior characteristics of GH2132 at different temperature(25??800?)and strain rate(0.001 s-1,4000 s-1?10000 s-1)were studied,and the constitutive model of the alloy under high temperature and strain rate was finally modeled.Under quasi-static condition,GH2132 had a work hardening and unconspicuous yield stage.Under high temperature and high strain rate,GH2132 showed a significant temperature softening effect.When the strain rate was between 4000 s-1?8000 s-1,the material exhibited strain rate strengthening effect while further increase the strain rate to 10000s-1,strain rate softening effect was shown.The built model was verified to be able to effectively describe the stress flow behavior of GH2132 under high temperature and high strain rate,and it was suitable for the finite element simulation of the alloy cutting process under relatively lower cutting speeds.There are 62 figures,20 tables,91 references in the thesis. |
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