Research Of Chemical/Electrochemistry Leveling Mechanism Based On 3D Printed Titanium Alloy Parts Surface

Titanium alloy has the advantages of high specific strength,good corrosion resistance and good biocompatibility.It has good application prospects in the fields of aerospace,shipbuilding,medical treatment and sports life.The use of laser additive manufacturing technology can make the structure complex titanium alloy parts.Now,it has become a research hot spot.However,due to the process characteristics of laser additive,it produces shortcomings such as microcracks and unmelted metal powder particles on the surface of titanium alloys,resulting in large roughness and poor corrosion resistance.Based on this,surface chemical and electrochemical leveling mechanism,which has an important theoretical and practical significance to optimize the surface of titanium alloy polishing process and improve its corrosion resistance.In this thesis,the surface activity of titanium alloy was studied by chemical method.The corrosion rate and surface roughness of titanium alloy were analyzed by electronic balance and roughness meter.The mechanism of titanium alloy surface leveling was discussed by electrochemical method.The scanning electron microscopy(SEM)and atomic force microscopy(AFM)was used to observe the surface topography and determine the composition of the film.The effects of the current density,time,temperature,cathode and other factors on the surface morphology,roughness,removal rate and electrochemical performance were analyzed.Tensile test and X-ray diffraction method were used to study the mechanical properties of titanium alloy after different treatments,and the following conclusions were obtained:In the chemical treatment process,the reaction time and the solution temperature on the titanium alloy surface condition and corrosion resistance are more significant.NH4HF2 solution and HF solution system can make the surface roughness Ra of the titanium alloy reduced by 1.8-2.0 ?m.However,the HF solution eroded the surface of the titanium alloy more seriously with more small pores.However,the corrosion rate of the titanium alloy film obtained by the finishing of the NH4HF2 solution is small,the capacitance resistance value is larger,and the corrosion resistance is stronger.From this,it can be concluded that the effect of NH4HF2 solution on the titanium alloy is more obvious,which the better process conditions were:NH4HF2(24%)165 ml·L-1,H2O2(30%)365 ml·L-1,C6H12N4 65 ml·L-1,HNO3(65%?80%)365 ml·L-1,additive(glycerol:glacial acetic acid:pyridine 5:3:2)33 ml·L-1,temperature of 30?,treating time of 10 min.After chemical treatment,the tensile strength and yield strength of the titanium alloy are higher than the conventional forgings.In the electrochemical treatment process,anhydrous ethanol solution and perchloric acid solution can make the titanium alloy surface roughness Ra reduced by 9.68?10.68 ?m,determine the two solution system better process conditions.The process conditions of anhydrous ethanol solution were 700 ml·L-1 of anhydrous ethanol,300 ml·L-1 of isopropanol,60 g·L-1 of aluminum chloride and 250 g·L-1 of zinc chloride.The current density is 0.26?0.28 A·cm-2,temperature of 30?,treating time of 15 min.Perchloric acid solution conditions were 82 ml·L-1 of perchloric acid,820 ml·L-1 of glacial acetic acid,98 ml·L-1 of water,the current density is 0.27?0.30 A·cm-2,temperature of 30?,treating time of 15 min.For the anhydrous ethanol solution system,titanium alloy surface erosion is more serious,poor finishing effect,but the corrosion resistance of the formed film is stronger.However,for the perchloric acid solution system,the finishing effect of titanium alloy is better,but the weight loss rate and thinning rate are slightly higher.At the same time,the tensile strength and yield strength of the titanium alloy are decreased after electrochemical treatment with the increase of polishing time.