Fundamental Research On Laser Oxidation Assisted Micro Milling Of Cemented Carbide

Cemented carbide is a very important material in the field of modern manufacturing industry due to its excellent performance.It is widely used to manufacture precision mould for optical glass parts and metal tension,and has broad market prospect.But cemented carbide also is a difficult to machine material because of its high hardness,good wear resistance and poor toughness.At present,there are many problems in micro milling of cemented carbide,such as high cutting force,severe tool wear and poor surface quality.Based on the high temperature oxidation mechanism and the temperature field simulation of laser radiation,this paper proposes a compound machining technology of laser oxidation assisted micro milling of cemented carbide.This paper is focused on the fundamental experimental study of high efficiency,high quality and long tool life micro milling of cemented carbide,the main work are as follows:(1)Based on the oxidation thermodynamics,high temperature oxidation experiments were conducted,and the changes of microstructure and chemical composition of cemented carbide material after oxidation was analysed.In the high temperature environment,cemented carbide material is severe oxidized.A honeycomb and porous oxidation layer is formed on the material surface.This greatly weakens the material hardness and strength.(2)The temperature field simulation model of cemented carbide under the laser radiation was established.After the correction of laser absorptivity,the influence of laser parameters on the temperature field was analysed.With the laser radiation experiments on cemented carbide,it is found that under laser radiation cemented carbide material not only undergo physical change of softening,melting and so on,but also happen chemical change of oxidation.With some laser parameters,the chemical change of oxidation even is dominant,and results in a porous oxidation layer on the material surface.Therefore,the cemented carbide oxidation of controllable range can be achieved with the laser radiation.(3)A compound machining technology of laser oxidation assisted micro milling of cemented carbide was proposed.First the laser radiation is used to induce the cemented carbide material oxidation,and form an oxidation layer of porous and easy to machine,then the cemented carbide material is removed with micro milling.In the micro milling experiments of cemented carbide,the change and influence in machinability performances of cemented carbide after oxidation was analysed.It is found that without affecting the surface roughness the compound machining technology of laser oxidation assisted micro milling of cemented carbide not only can greatly decreases the cutting force,but also can effective reduce the tool wear.(4)Ductile micro milling experiments of cemented carbide were conducted,and the formation mechanism and damage behavior of ductile machined surface were studied.A strategy on the parameters selection in ductile micro milling of cemented carbide was proposed.The appropriate increase of micro milling parameters,as long as the uncut chip thickness of the residual area is less than the critical uncut chip thickness,the defects formed by brittle fracture can be removed in the subsequent cutting,the ductile cut surface of high quality can be achieved as well.The tool wear performance of PCD micro milling tool also was discussed.The tool wear has important effects on the cutting force,surface roughness and the bottom width of machined groove.