| Nickel-base superalloy GH4169is commonly used to produce aerospace engines andgas turbine wheel, blades and other heat-resistant parts, due to its high strength, highstability and anti-fatigue properties at high temperature. With the rapid development ofthe domestic power industry, large-scale power stations have been established, and thedemand of gas turbine is increasing. However, the poor machinability of GH4169,which is represented by the special law in chip formation, cutting force, cuttingtemperature and tool wear in machining GH4169, leads to low cutting efficiency andrestricting its wide application severely. The high-efficiency cutting technology ofNickel-base superalloy GH4169is one of the urgent problems in today’s manufacturing.Therefore, the research on high-efficiency cutting technology of GH4169and its relatedmechanism have theoretical significance and wide application value.The chip formation process was studied by getting chip root. With the researches ofthe formation of built-up-edge (BUE) and its effects on chip formation, the cuttingdeformation mechanism was studied. The opinion that serrated chip formation processincludes three stages (primary, transition, and the last stage) was proposed. In thecutting process, the shear plane changed into ‘shear body’ with the decreasing of theshear angle. The serrated chip generated under the combined action of fracture andadiabatic shear. The model involving deformation of shear band based on the geometrycharacteristic of serrated chip was established. The effects of cutting parameters on thegeometry characteristic of serrated chip were also studied at last.The TiAlN coating and favorable tool geometry were chosen through cuttingexperiments and FEM in terms of tool material, cutting force, cutting temperature, toolgeometry and tool life. The physic process of tool material peeling off from toolsubstrate was studied though observing tool wear morphology and its features analysis,and the tool wear mechanism in machining GH4169was revealed. In machiningGH4169using PVD-film carbide tool, the BUE easily generated at low cutting speedand its falling off causes tool chipping. When cutting speed increased, tool substratematerial peeled off in the form of lamellar wear debris. This is the main form leading totool wear. The diffusion and oxidation between tool and chip/workpiece made thedensity of wear debris increase and then accelerating tool wear. The model representingtool wear process was established in the light of cutting theory and friction wear theory.Based on the research of tool wear mechanism, the adhesion, diffusion and oxidationwear is considered as the characteristics of slide wear. The delamination theory ofsliding wear was used to analyze the plastic deformation and fracture behavior of metallic materials which is closed to the tool surface. Tool flank wear model wasestablished considering the mechanical property changes of tool material, and the wearmodel was verified through experiments.For each pair of the tool-workpiece, there exists an optimal cutting temperature tomake the strength ratio of tool-workpiece material maximum in cutting process. Theoptimal cutting temperature was calculated in the light of the established wear model, inorder to make the cutting length longest when tool fail. Excellent experimentalagreement was achieved in optimal temperature calculated by the established model.The empirical model using cutting parameters at the optimal cutting temperature wasestablished using the least squares method. The thermostatic cutting method wasproposed to provide an effective and rapid method for the reasonable choice cuttingparameters. Finally, the surface roughness was used to evaluate the feasibility ofthermostatic cutting technology. The results show that thermostatic cutting technologyhelps to select the cutting parameters, reduce the surface roughness value and improvecutting efficiency, in accordance with the development trends of high-efficiency cuttingtechnology. |
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