Study On Machinability And Surface Quality Of FeCoNiCrMn High Entropy Alloy By Ultrasonic Assisted Milling

Since Ye Junwei put forward the concept of high entropy alloy in 2004,high entropy alloy has aroused the research upsurge of scholars all over the world.Compared with traditional alloys,high entropy alloys had excellent properties,such as high hardness,high specific strength,high impact resistance,high wear resistance and high corrosion resistance.At present,a variety of alloy systems have been developed,mainly high entropy alloys of group 5-7 principal element,among which FeCoNiCrMn high entropy alloy,as the earliest system defined as high entropy alloy,has been systematically studied in recent years.However,in the machining of high entropy alloy,there were more scratches on the machined surface and obvious work hardening phenomenon,which led to poor surface quality and serious tool wear during machining.Ultrasonic vibration assisted cutting has the characteristics of tool/piece,tool/chip phase separation and impact in the cutting process,which makes it beneficial to reduce cutting force,improve chip formation and improve surface integrity in the machining process.Therefore,the ultrasonic vibration assisted milling method can solve the problems in the machining process of high entropy alloy,and lay a foundation for the wide application of high entropy alloy.In this study,FeCoNiCrMn high-entropy alloy was taken as the research object,and three different cutting tools were selected to process FeCoNiCrMn high-entropy alloy.The machinability of FeCoNiCrMn high-entropy alloy was studied,the matching performance between cutters-workpiece materials and the service life of cutting tools were analyzed,and the cutting tools suitable for processing the high-entropy alloy were selected.The optimal machining parameters and vibration parameters were determined by orthogonal cutting experiments,and the influence of technological parameters on surface quality was analyzed.The main research contents were as follows:Firstly,three end milling cutters were selected to process FeCoNiCrMn high entropy alloy with the same processing parameters.The cutting force,cutting temperature,chip,surface roughness,surface morphology,hardness and so on were compared and studied.The results show that the cutting force,cutting temperature and surface roughness of the TiAlN coating tool have the lowest work-hardening phenomenon in milling FeCoNiCrMn high entropy alloy compared with TiAlCr N and ultra-fine crystal tool.TiAlN coating tool has comparative advantage in processing FeCoNiCrMn high entropy alloy.Furthermore,the effects of different cutting parameters and vibration parameters on the machinability of FeCoNiCrMn high entropy alloy were investigated by orthogonal experiment with TiAlN coating tool.It is found that cutting depth has the greatest effect on cutting temperature,ultrasonic vibration could play a role in reducing cutting temperature,spindle speed has the greatest effect on tool wear,high speed will aggravate tool wear,applying ultrasonic vibration could reduce the tool wear speed in milling process.The introduction of ultrasonic vibration could alleviate the phenomenon of work hardening.The spindle speed has the greatest influence on chip length.The larger the rotational speed is,the smaller the chip length is.The application of ultrasonic vibration will produce dense folds on the non-free surface of chips,and the application of moderate ultrasonic vibration could reduce the cutting force.Finally,the surface quality obtained by orthogonal experiment is further studied.The results show that the surface roughness is most affected by the feed rate per tooth,and the increase of the feed rate will increase the instability of the cutting process and lead to the increase of the roughness.The application of ultrasonic vibration with medium amplitude is helpful to reduce the surface roughness level,mainly because it increases the stability of the cutting process.The influence of ultrasonic vibration on the surface texture volume exceeds its influence on the surface roughness.The application of ultrasonic vibration could produce small ripples on the surface texture formed by traditional milling,but the high spindle speed will make this effect no longer obvious.The application of ultrasonic vibration could also reduce the production of surface defects in the machining process.Ultrasonic vibration has a great influence on the surface contact Angle.The main reason is that ultrasonic vibration assisted milling could help to form regular surface topography of the machined surface.Considering the processing efficiency and quality,n=6000r/min,fz=6μm/z,ap=0.15 mm,A=6μm are the best parameters.