Study On Thermal-Assist-Machining Of Superalloy Based On Contacting Friction Characteristics Between Tool And Workpiece

Superalloy is widely used in the aerospace field because of its excellent high temperature mechanical properties,oxidation resistance and corrosion resistance.Superalloy is known as a kind of difficult-to-machine material,so its machining efficiency is low and cost is high.To improve the machinability and efficiency of superalloy to reduce costs,and consider to be combined with the hybrid additive and reductive manufacturing method in furture,thus this research was carried out in this paper.To provide experimental and theoretical basis for choosing cutting tool material and explain the friction characteristics of cutting tool-workpiece under high temperature,the friction characteristics and wear mechanism between typical cutting tool materials and superalloys are explored.The machinability of superalloy and the wear mechanism of cutting tool are explored through the thermal-assist-machining,and the effects of the preset temperature of workpiece on the cutting behavior,the cutting force,the temperature field distribution and the stress in the cutting process are analyzed by simulation,which provides the theoretical basis for the optimization of the cutting tool and the processing parameters of superalloys.The friction and wear characteristics of the typical tool materials and the superalloy are studied.Different sliding speed and load were used at different temperatures to explore the friction and wear characteristics between typical tool materials and superalloys,and the effects of temperature on the friction characteristics between the tool material and the superalloy were investigated emphatically.With the increase of temperature,the friction coefficient of the frictional pair and the vibration in the friction process decreased,the wear mechanism of the tool material was changed from the adhesive wear and abrasive wear at room temperature to the oxidation wear and diffusion wear at high temperature.The wear rate order of the tool material with the GH2132 frictional pairs and GH4169 frictional pairs is WC>SiC>Si3N4 at 800 ?.The wear rate order of the tool material under the same test conditions is SiC>SiC>WC.A reasonable finite element model was established to simulate thermal-assist machining of superalloy.Based on the simulation results,thermal-assist-machining of superalloy process were analyzed and discussed.As the preset temperature of workpiece increases,the stress on the workpiece and the tool decreased during the cutting process,and the gradient of stress on the tool surface decreased.The chip morphology was different at different preset temperatures:the chips were saw-tooth shaped chip at room temperature and 400 ?,and the chips were continuous chip at 600 ? and 800 ?.The cutting force and the amplitude of the cutting force decreased as the temperature of the workpiece increased.The change of the preset workpiece temperature has no obvious effect on the maximum temperature value of the chip during the cutting process,and has a great influence on the temperature field distribution.The maximum temperature of the tool surface decreased with the increase of the temperature of the workpiece,the distribution of the temperature field on the tool surface was not changed,and the temperature gradient decreased with the increase of the initial temperature.During the cutting process,the strain rate and strain of the workpiece decreased with the temperature of the workpiece.Based on the friction and wear test and the simulation,a kind of thermal-assist-milling method and device was designed and used to explore the cutting performance of superalloys under the high temperature condition.Under the guidance of the friction and wear test,the the silicon nitride ceramic cutting tool,the Sialon(silicon nitride-based ceramic)ceramic cutting tool and cemented carbide cutting tool were used to milling nickel-based superalloys under high temperature conditions.The wear characteristics of the cutting tool under different temperature conditions were compared and analyzed.At high temperature the wear of cemented carbide cutting tool is more serious than room temperature conditions,the adhesive wear increased with the preset temperature of workpiece increased.The wear of the silicon nitride ceramic and the Sialon ceramic cutting tool decreased with the preset temperature of workpiece increased.The notch wear and the peeling of the tool were gradually disappeared with the increase of the preset temperature of the workpiece.Under the same conditions,the wear of the Sialon ceramic tool was less than that of the silicon nitride ceramic tool.