| Surface micro-texture technology originating from the surface microstructure of animals and plants has become one of the important means to improve the friction and wear properties of materials.The results show that micro-texture can significantly improve the cutting performance of cutting tools.In recent years,the application of micro-texture in cutting tools has become a research hotspot of scholars at home and abroad.Due to the advantages of high power density and high processing accuracy,the micro-texture of cemented carbide tools is widely fabricated by laser processing technology.However,in the process of laser fabrication of cemented carbide tools,the influence of laser on the thermodynamic properties of cemented carbide such as ablation at high temperature,oxidation and thermodynamic fatigue has not attracted enough attention.The effects of laser fabrication on the microstructure and properties of micro-textured tools and friction and wear properties need to be solved urgently.Therefore,the research and development of micro-texture cutting tools not only has high academic value,but also has great engineering significance.In this paper,the formation mechanism,morphology and microstructural changes of HAZ on the surface of cemented carbide during laser microtexturing are studied by means of computer simulation and experimental study.The effects of laser processing on the microstructure and morphology of HAZ and the microstructural properties of HAZ materials are revealed.Rule of sound.The effects of these changes on the friction and wear properties of micro-textured cutting tools are analyzed and experimentally studied,and the influence of laser processing parameters on the friction coefficient of micro-texture is obtained.Finally,by studying the influence of micro-texture on cutting performance,the optimization design of micro-texture parameters of cutting tools is carried out.The micro-texture morphology and structure and properties of heat-affected zone are controlled by laser processing parameters,and the anti-friction and anti-wear properties of micro-texture cutting tools are improved.The main research contents and conclusions are as follows:(1)The effect of laser on cemented carbide material is simulated by heat conduction equation.The power density distribution under different laser processing parameters is compared.The temperature field distribution in laser processing cemented carbide is simulated and calculated,and the distribution rule of heat affected zone is found.The simulation results show that the temperature in the central region of the heat affected zone is the highest,and the temperature distribution from the central region to the edge region is gaussian.The threshold of laser ablation of YG8 cemented carbide is predicted.The simulation results show that when the laser is applied on the surface of cemented carbide,when the temperature exceeds the melting temperature of cemented carbide,a small part of the surface of the material will be gasified and most of the surface will be melted.When the laser action stops,the heat is still diffused into the cemented carbide with a certain temperature gradient and dissipates gradually.Among them,laser power density is a significant factor affecting the scale of heat affected zone,followed by laser scanning speed and scanning times.(2)An experimental platform for laser processing of micro-textured cemented carbide cutting tools was established.The effects of laser processing parameters(laser power,scanning speed,scanning times)on the microstructure and properties of micro-textured HAZ cemented carbide materials were studied experimentally.The change rule of microstructure of micro-textured HAZ cemented carbide materials under laser was revealed.The effects of different laser processing parameters on the two-dimensional and three-dimensional morphologies of micro-textures were studied.The microstructure and elemental composition of the heat-affected zone around each type of micro-textures were observed.The micro-hardness,nano-hardness and micro-cracks of the heataffected zone were also studied.The results show that the oxidation degree of cobalt decreases with the decrease of temperature from the central region to the edge region of the heat affected zone;the grain size of WC decreases in the heat affected zone;the microhardness increases with the increase of laser power density and scanning times;and the positive effect of laser-processed micro-texture on the cutting performance of cemented carbide tools(i.e.,surface friction decreases,wear resistance)Improvement)is the result of surface modification of HAZ.(3)Based on the simulation process of micro-texture friction and wear in heat-affected zone(HAZ)treated by laser,the finite element simulation of microtexture friction and wear surfaces with and without texture was carried out.The results show that micro-texture surfaces can reduce friction and wear during friction and wear,and the distribution of surface stress state is relatively uniform.Secondly,a disk-pin friction and wear test platform for cemented carbide microtexture was established.The influence of laser processing parameters on the friction coefficient of micro-texture was revealed through orthogonal friction and wear tests.Among them,laser power has the most significant effect on the friction coefficient of micro-texture surface,followed by scanning times and scanning speed.The optimum laser processing parameters in orthogonal experiment are obtained by range analysis.Finally,based on the surface modification of heat-affected zone,the mechanism of further friction reduction of micro-texture is analyzed.(4)The effect of micro-texture parameters on cutting Ti6Al4 V by microtexture cutting tools was systematically studied,and multi-objective optimization of micro-texture parameters was carried out with cutting force and cutting temperature as objectives.Firstly,the finite element simulation model of Ti6Al4 V cutting with micro-texture cutter is established,and the variation law of cutting force and cutting temperature is obtained when micro-texture cutter cuts Ti6Al4 V.An experimental platform of micro-texture cutting tool was built.The cutting force and temperature changes of YG8 micro-texture cutting tool when cutting Ti6Al4 V were obtained through experiments.The results show that the main factor affecting the cutting force of micro-texture turning blade is the diameter of micro-texture,followed by the depth of micro-texture,and the distance between micro-textures has the smallest effect.The most important factor affecting the cutting temperature of micro-texture turning blade is the depth of micro-texture,followed by the distance between micro-textures,and the distance between micro-texture and cutting edge has the smallest effect.Based on the cutting performance and the lubrication of cobalt oxide,the wear resistancemechanism of micro-textured cutting tools is comprehensively analyzed.Finally,the mathematical model of cutting force and cutting temperature is established,and the genetic algorithm is used to optimize the micro-texture parameters of the tool.With the minimum cutting force and the minimum cutting temperature as the optimization objective,the optimal results of the diameter,depth,spacing and distance from the cutting edge of the micro-texture are obtained.The research results lay a good foundation for the project of laser-assisted cemented carbide micro-texture cutting tools,and provide ideas for the application of cemented carbide micro-texture in a wider field and the development of advanced cutting tools. |
