| Cemented carbide has excellent mechanical properties and is widely used in strategic pillar industries such as machining and aerospace.Especially in the cutting tool industry,it has a dominant position.As a typical brittle and hard material,its mechanical properties are extremely sensitive to microstructures,especially various macro-micro defects.Small defects or local material weakening can easily expand in a wide range under the drive of cutting loads,especially thermal loads,causing tool damage,resulting in production interruptions,and even threatening production safety.In order to meet the increasing requirements of high-efficiency and high-precision cutting,this article takes YT5 carbide tools commonly used in heavy-duty cutting as the main research object,and accurately characterize the evolution of the microstructure of the tool during the cutting process,ascertain its safe service load,and reveal the physical nature of its mechanical performance degradation,and maximizing the performance potential of this material has become a common focus of attention in the field of metal cutting and material research and development.This paper uses multi-scale characterization technology to systematically study the unique organizational structure of tool materials at various scales.Based on multi-scale characterization test data,combined with ICME's multi-scale fusion modeling concept,a handshake area model that can effectively describe the microstructure characteristics of cemented carbide is constructed.Effectively realize the prediction of tool mechanics.Based on the principle of thin film thermocouple temperature measurement,a new wireless temperature measurement tool system was developed.Use finite element simulation to detect the tool rake face force-thermal load distribution to determine the deposition position of the thin film thermocouple;Use femtosecond laser technology to process the deposition groove on the surface of the cemented carbide tool,and apply electrolysis-plasma polishing technology to perform surface quality treatment on the bottom of the deposition groove;Plasma-enhanced chemical vapor deposition method is used to plate insulating coating in the deposition tank,and Ni Cr/Ni Si temperature measurement coating is plated by magnetron sputtering method.Then the static calibration method was used to verify the temperature measurement accuracy and sensitivity of the temperature measurement coating,and the cutting test was used to verify the cutting performance of the temperature measurement tool.Finally,referring to the actual working conditions of the enterprise's production and processing,an equivalent interrupted cutting test was carried out,combined with FEM,to detect the cutting temperature distribution of the tool surface under typical working conditions,and to obtain samples to be characterized at different stages of the damage evolution of the bond damage.For the tool-chip interface in the sample,use SEM to observe and analyze the microstructure,fracture morphology and element distribution on the micrometer scale;use EBSD to study the grain size and texture strength;using ACTEM to study the crystal/phase boundary structure and its defects before/after tool damage on the submicron and nanometer scales;use SAD and fast Fourier transform spectroscopy of HRTEM images to study the phase and phase relationship of the local specific microstructures of the sample;use ACTEM-EDS to accurately characterize the distribution of phase boundary elements and the deposition of microstructures;HRTEM is used to characterize the phase boundary structure and phase boundary defects of WC/Co at the atomic level.The results provide effective support for the research on tool damage mechanism,especially the damage mechanism.Based on the HRTEM image of the WC/Co interface,and construct WC/Co?and WC/Co?interface models with three-dimensional periodic boundary conditions.First-principles calculations are used to study the influence of the martensitic transformation of the binder phase and the impurity segregation caused by the diffusion of cutting elements on the interface stability and fracture performance,through comparative study of WC/Co?and WC/Co?interface performance,and reveals the physical nature of the mechanical properties of cemented carbide attenuation,and provides a basis for the subsequent establishment of a model that effectively links the microstructure and macro-mechanical properties of cemented carbide.Based on the multi-scale characterization test data,combined with the ICME concept,a“bottom-up”cemented carbide multi-scale model construction plan is proposed.Using the Cohesive element model,based on the first-principles calculation data,a two-dimensional finite element model of the WC/Co,Ti C/Co interface on the micro scale was constructed,and the interface strength was calculated.Using thermal shock test,combined with SEM analysis,the effect of different loading temperatures and loading methods on the porosity of the tool is calculated,and the obtained porosity is substituted into the WC/Co interface FEM model,and studied the influence of different types and distribution of micro-defects on the strength of the interface.Using the Voronoi algorithm,a handshake area model that can effectively connect the microstructure of the material with its macro-mechanical properties is built.Subsequently,the equivalent elastic modulus was used as the evaluation index to determine the representative volume unit model of cemented carbide.Based on this model,a prediction method of tool hardness is proposed. |
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