Research On Element Diffusion And Tool Failure Of The Cemented Carbide Tool Cutting 2.25Cr1Mo0.25V Material

2.25CrlMo0.25V material has high thermal strength,excellent corrosion resistance and good stability,and is widely used in large-scale hydrogenation reactors for coal liquefaction equipment in the petrochemical industry.During the cutting process of this material,it will cause the element diffusion at the tool-chip interface due to the high temperature and high pressure on tool rake face,resulting in the formation of metamorphic layer on the rake face,and the metamorphic layer makes the tool and chip adhere together,which it the reason why it's called adhering welding layer.The adhering welding layer is diffeerent from the tool matrix in its surface hardness,crystal surface energy,crystal boundary cohesion and other physical properties,and those properties are weakened,leading to the rake face is prone to crack,which will result in the aggravation of tool wear or the occurrence of bonding breakage,so the problem of tool failure is prominent.So based on the effect of temperature on element diffusion of the cemented carbide tool rake face,the quantitative relationship between tool-chip element diffusion concentration and wear rate is established,and micro-mechanism and macroscopic properties are studied by combining with 3D model of adhering welding layer micro-crack propagation and macroscopic finite model of adhering welding layer peeling.In order to study the temperature distribution law on rake face of tool with adhering welding layer when cutting 2.25CrlMo0.25V material,based on the composition of adhering welding layer on rake face,a theoretical model of heat transfer with or without adhering welding layer on rake face is established by combining the determined equivalent thermal conductivity of adhering welding layer with heat conduction theory,and the feasibility of the model was verified by cutting temperature experiment,numerical simulation and simulation analysis.Based on this,the effect of the existence and thickness of the adhering welding layer on the temperature distribution and gradient change of the cemented carbide tool rake face was studied,which lays a theoretical foundation for the subsequent research of the diffusion behavior of the tool-chip elements in the tool rake face.The experimental scheme of diffusion couple for clamping workpiece and welding workpiece at different temperatures is proposed based on the formation mechanism of adhering welding layer.The initiation and development process of adhering welding layer are simulated through this experiment,and the effect law of temperature and adhering welding layer on the element diffusion concentration and diffusion rate are studied based on this.Then according to Fick's second law,the element concentration of tool-chip on tool rake face is obtained,and combined with semi-infinite length model,the tool-chip elements diffusion equation is established to obtain the distribution law of main element concentration on tool rake face at different temperature.In order to further study the influence of element diffusion on tool rake face,the micro-structure parameters of Co,WC and TiC are determined by stereological principle.The WC particles generated by Voronoi polyhedron are combined with MPT toolbox of MATLAB software and ABAQUS software to create a 3D structure model of the cemented carbide tool rake face,and the constitutive relationship of Cohesive unit is compiled by Python language.The 3D micro-crack propagation model of cemented carbide tool rake face is established,and the propagation law of different crack types and paths on the tool rake face are revealed,and the effect law of crack on the tensile strength is explored.Aiming at the diffusion wear problem of the cemented carbide tool rake face,the basic data of the diffusion concentration of the tool-chip element is obtained by the static diffusion experiment of tool and workpiece material under clamping,combining it with the elemental diffusion concentration law of the chip contact area during the cutting process,the theoretical model of the diffusion wear of the internal elements in the tool is established.According to the correlation between the maximum wear rate of the tool rake face and the element concentration,the prediction of the wear rate on tool rake face is completed.Finally,by studying the position and stress state of the flank of the tool rake face during interrupted cutting and continuous cutting,the Cohesive element constitutive model is used to establish the macroscopic simulation model of the adhering welding peeling on the tool rake face and analyze the effect of the crack type and load on the adhering welding layer.In summary,this paper studies the element diffusion and tool failure during cemented carbide tool cutting 2.25CrlMo0.25V material,and analyzes the temperature distribution of tool rake face and the element concentration distribution of tool-chip interface.Meanwhile,the relationship model between element diffusion concentration and wear rate is established,and the crack propagation characteristics in the adhering welding layer formed by element diffusion are explored,and the effect of cracks on adhering welding layer peeling is obtained,which are of important theoretical value and practical significance for further revealing the failure mechanism of cutting tools,improving the service life of cutting tools,and enriching and perfecting the design of cutting tools.