Research On Material Removal Mechanism And Machining Performance Of Short Electrical Arc-Electrochemical Compound Machining Titanium Alloy

As one of the high-efficiency electrical discharge machining technologies,short electrical arc milling(SEAM)processing technology is mainly aimed at the machining of parts and components of difficult-to-cut materials such as titanium alloys and high-temperature alloys.Because SEAM processing is a non-contact processing technology,it is not affected by the strength,hardness,toughness,and brittleness of the machined materials.It has the advantages of high machining efficiency and low economic cost,so it has unique advantages for the efficient processing of such difficult-to-cut materials.However,due to defects such as high surface roughness,recast layer and heat-affected zone on the surface of the workpiece after SEAM,which seriously affects the surface quality of the machined workpiece and the timeliness of subsequent processing procedures.Therefore,the problem of low surface quality in SEAM processing difficult-to-cut materials has not yet been effectively solved.Because the SEAM process is not only affected by the combined effects of electric field,flow field and other multi-field coupling,but also involves multiple chemical and physical processes such as electrochemistry and molecular dynamics,which results in the micro-geometric characteristics of the machined surface and the physical and chemical properties will change,and the electrochemical effect existing the inter-electrodes will have a certain removal effect on the recast layer and the heat-affected zone.Therefore,this thesis proposes a short electrical arc-electrochemical compound machining method based on NaCl solution to improve the surface quality of SEAM.This thesis first improved the working medium flushing circulation system in the processing platform,and then proposed the short electrical arc-electrochemical compound machining(SEACM)method,and analyzed the SEACM machining principle,and then carried out the SEACM machined Titanium alloy TC4 experiment by setting different machining parameters.The experimental results show that the mechanism of material removal inter-electrodes is changed from pure SEAM to hybrid SEAM/ECM under a certain solution conductivity and low feed rate,so the surface roughness,recast layer thickness and heat-affected zone thickness of the processed workpiece can be effectively decrease.In addition,increasing the voltage and duty cycle can also effectively reduce the recast layer thickness.In order to deeply research the machining performance and surface integrity of SEACM machined Titanium alloy TC4 in NaCl solution,single factor experiments were used to study the effect of different processing parameters(these parameters include voltage,duty cycle,solution conductivity and feed rate)on the material removal rate(MRR),surface roughness(Ra),the three-dimensional profile of the workpiece surface and the thickness of the recast layer.Subsequently,the gray correlation degree analysis method in gray theory was used to establish a gray correlation degree matrix.According to this matrix,the analysis of the influence of different processing parameters on the surface roughness of the workpiece and the thickness of the recast layer was carried out.Finally,for the multi-objective decision-making problem of optimizing the process parameters of the surface integrity of the SEACM machined workpiece,the gray situation decision-making theoretical method and model were used to give a situation effect sample and establish a satisfactory situation based on the unified measurement space.The optimal combination of process parameters for the surface integrity of the workpiece were obtained.