Study On Wear Characteristic Of TiCN/Al₂O₃ Composite Coated Tool In Machining Natural Marble

The natural marble is a typical hard brittle diffcult-to-machine material.Due to the low machining accuracy and high cost,the electroplated tool and sintered diamond cutting tool can not meet the high-grade and special-shape needs of the modern stone products.In recent years,the composite coated tool is gradually being used in high-grade stone products machining field for its excellent cutting performance.However,the advantages of the coated tools are not fully exerted due to the lack of theoretical and experimental research in the wear field of coated tool.In this thesis,the wear characteristics of TiCN/Al2O3 composite coated tool in cutting natural marble was taken as the research object,the problems such as wear force and wear mechanism were reaearched.The friction and wear theory of coated tool material in the machining process of natural marble were analysed.Combined with the removal mechanism of natural marble,the five different stages of the friction characteristics during the process of machining were put forward.The view of friction coefficient of coated tool was a three component function of surface roughness of natural marble surface,adhension and furrows on the flank face of cutting tool.Based on the analysis,the tool wear process of coated tool can be divided into three important processes of adhesive effect,surface fatigue and surface damage.The expression of tool wear rate was built.According to the expression,the wear rate is mainly influenced by the fracture toughness,hardness of the coating material and the tool substrate material.In the process of coated tools machining natural marble,the geometry model was built based on the characteristics of milling tool.The theory model of cutting force was set up by the infinitesimal analysis method.The theoretical calculate formula was obtained by integration.The cutting force simulation of coated tool cutting natural marble was built by using DEFORM-3D.The natural marble processing test system was built which including special shape stone turn-milling center,TiCN/Al2O3 coated tool,cutting force detection system and data processing system.The cutting force information of natural marble milling process under different parameters was based on the data measured in the experiment.Contrastive analysis on the simulation data and pratical cutting data were carried out.Results showed that the relative error of cutting force is around 10%which verified the reliability of the simulation model.The change characteristics and regulartity of cutting force with different cutting parameters were obtained through the force data.Analysis showed that the appearance of brittle-ductile transformation reduces cutting force within a certain range when the cutting speed is highed,the increase of feed speed increases the cutting force,the variation trend is stable and the cutting status is perfect when the cutting depth is given as the cutting speed confined to 75.36-94.2m/min,the feed speed confined to 1000-1500mm/min under the experiment conditions of this thesis.The weared surface of cutting tool was observed by the scaning electron microscope.The wear extents of coated tool under different parameters were measured.The prediction experience formula of tool wear extent was established according to the wear extent data.The influence charateristics of different processing parameters on coated tool wear extent was analysed.Results show that the wear extent decreases with the increase of spindle speed which means cutting speed,the wear extent increases with the increase of feed speed and cutting depth.The wear morphology characteristics and the wear mechanism of coated tools were illustrated according to the SEM morphology image and spectrum detector results of weared tools.Analysis shows that the wear mechanism of coated tools can be divided into adhesive wear,abrasive wear,fatigue wear and fretting wear,the fretting wear is a kind of composite wear form.The transition characteristics of wear mechanism under different cutting parameters were analysed,the transition of tool wear mode has a direct correlation with change characteristics of cutting force and the origin reason of the transition is the change of cutting parameters.Finally,the optimization suggestion of coordination selection of cutting parameters in actual machining was put forward.