Research On The Method And Process Of Micro Milling Titanium Alloy Assisted By Plasma Electrolytic Oxidation

Titanium alloys have meaningful application prospects in aerospace,biomedical,petrochemical and other fields because of its high specific strength,low density,excellent extreme temperature resistance and corrosion resistance.However,due to the low elastic modulus and thermal conductivity of titanium alloys and high chemical activity at elevated temperature,it is difficult to solve the problems of low efficiency,serious tool wear and poor surface quality in conventional micro milling of titanium alloy.To solve this problem,starting from reducing the strength of the material to be milled,this paper puts forward the idea of in-situ growth of gloomy strength loose ceramic film on the surface of Ti6Al4V alloy by plasma electrolytic oxidation technology.The purpose aims to reduce the cutting load to control the tool wear speed,so as to extend the tool life,improve the surface quality and optimize the milling parameters.The main research contents and conclusions are as following:(1)Based on the double action mechanism of plasma and electrolyte on the film surface during plasma electrolytic oxidation,three kinds of electrolytes with phosphate,aluminate and silicate as main components were designed,and three kinds of low strength loose ceramic films with different salts were obtained.The effects of different electrolytes on the structure and properties of the films under specific power parameters were investigated.The results show that the thickness of the three kinds of films is about 20?m,the structure is loose and porous,the adhesion with the substrate is poor,and the microhardness of the softest film is reduced to 18.4%of the substrate hardness.(2)On the basis of three kinds of low strength loose ceramic films prepared by plasma electrolytic oxidation,micro milling experiments were carried out on the films under dry milling conditions.By comparing with conventional milling,the effects of different films on milling force,tool wear,tip burr,chip and machined surface roughness were investigated.The results show that:Na Al O₂ is the main component of electrolyte The results show that the machining performance of the oxide film is the best,the three-dimensional milling force decreases most obviously,the tool wear rate decreases significantly,and the surface processing quality improves significantly.(3)In order to further improve the machining performance of low strength ceramic film by plasma electrolysis,the electrolyte ratio and power supply parameters of aluminate system were optimized by orthogonal experimental design and response surface design,and the influence of different electrolyte and power supply parameters on the thickness,hardness and roughness of the oxidation film was explored.Finally,the micro milling experiment of the optimized film is carried out,and the results show that the optimized film with higher thickness still has better machining performance.(4)The evolution process of plasma electrolytic oxidation low strength ceramic film was studied systematically.The growth process of the film was clarified,and the formation mechanism of the low strength characteristics of the film was revealed,which provided a theoretical basis for exploring the preparation methods of other low strength loose structure films.Combined with the growth process and mechanism of the film,the material removal mechanism of milling processing was further analyzed and discussed It points out the key work for the further optimization of film and the adjustment of milling parameters.In this project,a new clean and efficient micro milling process of titanium alloy is proposed,which reduce the machining difficulty of titanium alloy micro milling,lays a theoretical and experimental foundation for the application of plasma electrolytic oxidation in the field of micro milling of titanium alloy,enriches and develops the processing technology of titanium alloy,and promotes the application and improvement of titanium alloy in aerospace,biomedical and other fields The manufacturing level of a country is of great significance.