Tool Wear In High-speed Turning Of Superalloy Based On Fractal Theory

High-efficiency,high-performance and green processing have become the development trend and requirements of today’s manufacturing industry.Iron-based superalloy is a kind of difficult-to-machine material with high toughness,high plasticity and severe work hardening.Therefore,in order to reduce processing costs,promote green low-carbon production and meet old and new kinetic energy conversion needs,high-efficiency and high-quality processing of iron-based superalloy has become a hot spot in modern manufacturing industry,which has important guiding significance for the development of manufacturing industry in the future,and has a profound influence on promoting intelligent cutting processing.Based on fractal theory,this dissertation uses carbide coating tools to carry out experimental research on high-speed cutting iron-based superalloy.The changes of chip morphology and cutting force signal and their fractal characteristics,machining surface morphology and its fractal characteristics,tool life and wear mechanism,and tool wear morphology fractal characteristics are explored.The relationships between the fractal parameters and the cutting parameters and tool wear are established,which provide a theoretical basis for the prediction of tool wear during cutting.Firstly,a three-dimensional simulation model of tool-workpiece is established,the effective stress,temperature field of the workpiece and the tool,and the change of tool wear are studied,coated tool is selected preferably.The results show that the temperature and effective stress on the tool tip and the workpiece are increased with the increase of cutting speed,causing the tool wear rate increase continuously.The resultant cutting force is increased instantaneously and then fluctuates steadily during the cutting process,but it is firstly increased and then decreased as the cutting speed increases.Tool wear is mainly concentrated on the rake face,the wear rate is decreased first and then increased with the cutting process,and the Ti Al N/Al Cr N coating performance is more excellent.Secondly,through the high-speed turning test,the characteristics of chip morphology and cutting force signals and theirs fractal characteristics are studied,the relationship between the fractal dimension of chip morphology and cutting force signal and cutting parameters and tool wear is established.The results show that the chips are severely deformed and jagged,the degree of saw-tooth of chip is more and more obvious with the increase of cutting speed.The chip morphology has fractal characteristics,and its fractal dimension gradually increases with increasing cutting speed and tool wear,which can be used to predict chip morphology.The variation trend of the cutting force is corresponded to the change trend of the tool wear curve.The cutting force single curve has fractal features,its fractal dimension is increased gradually with increase of cutting speed,and reduced firstly and then improved with the increase of tool wear,which can predict the change of tool wear.Thirdly,the morphological characteristics of the machined surface and its fractal dimensions are explored,and the relationship between its fractal dimension and cutting speed and tool wear is constructed.The results show that the morphology of the machined surface is mainly characterized by side flow,build-up layer,and scratches,etc.The fractal dimension of machining surface contour curve is increased gradually with the increase of the cutting speed,and it is increased first and then decreases with the increase of tool wear.The fractal dimension of two-dimensional morphology is decreased gradually with the increase of the cutting speed,but as the tool wear increases,the fractal dimension of it is decreased at first and then increases,which can be used to predict tool wear and machined surface morphology.Finally,the tool life and tool wear morphology characteristics are analyzed,the tool wear mechanism is revealed,and the relationship between the tool wear morphology fractal dimension and tool wear is established.The research shows that,the coated cemented carbide tool life is greater than cermet tool.The main wear forms of the cutting tool are the rake wear and flank wear.The main wear mechanisms of the tool include abrasive wear,adhesive wear,and oxidative wear.The tool wear morphology has fractal characteristics,and its fractal dimension is increased firstly and then decreases with the increase of cutting speed,but decreases first and then increases with the increase of tool wear,which can predict tool wear.