Mechanism Of Chip Formation And Fracture Of PCBN Cutting High Temperature Alloy Under High-Pressure Cooling

Superalloy is widely used in different fields,for example aerospace,because its characteristics of high yield strength,structure stability,etc.under the environment of high-temperature with the good property of elevated temperature strength,thermostability and thermal fatigue.But it's a kind of typical difficult-to-machine material for its poor thermal conductivity,plastic toughness,service hardness of surface machining,and unbreakable chip,which all make high-temperature alloy possess a poor machinability property.PCBN tool is a new superhard cutting tool material and has a better advantage on high-temperature alloy process.But,PCBN tool usually doesn't have chip-breaking groove with its material property which leads the result of difficult-to-break-chip.Chips are hard to be broken by twining round workpiece and cutter during cutting,which shorten the service life of cutter and lower the quality of machined surface.High-pressure cooling is a new processing technique on metal machining with high-efficiency.It helps to improve the property and ability of chip-breaking,prolong the service life of cutter,and higher the quality of machined surface.This thesis is a study on chip curling and breaking mechanism by taking an experiment of Nickel-base superalloy GH4169 by PCBN tool under high-pressure cooling,and analysis of its breaking property.Firstly,study on cutting force and chip morphology by taking an experiment.Take coolant pressure,cutting parameter,cooling condition as variable parts to experiment,compare and analyze cutting force and chip morphology with different factors.With the high-pressure cooling condition,study on the influence rules and reasons of cutting force,analyze on change rules of chip morphology,chip curling and breaking.Secondly,analyze on Nickel-base superalloy chip formation mechanism during machining and study on the forming process of serrated chips.Set a prediction model on chip-curling radius according to the stress distribution of cutting region by analyzing force condition of chips,then set a chip-breaking model by taking the maximum scale strain theory as criterion.Analyze the bending influence rules of high-temperature alloy during cutting process and take the rules for a further study of chip-curling radius change and chip strain change to set the models under the condition of high-pressure cooling.Then study on chip micromorphology,concrete analyze the superficial characteristics of sawtooth-shape chips of Nickel-base superalloy and its changing rules under high-pressure cooling.Finally to verify all the theoretical analysis.At last,set a finite element simulation model of Nickel-base superalloy by PCBN tool under high-pressure cooling to simulate analyze the forming process of serrated chips and the influence rules of chip morphology and cutting force with different cutting parameters,cooling conditions and coolant pressures.At the meantime,conduct a simulated analysis of chip curling and breaking under the condition of high-pressure cooling,study on the performance of chip curling radius with the change of coolant pressure.Validate all the theoretical analysis with the simulated results and provide a theoretical basis for the future study on high-pressure cooling process.