Study On Friction Electrochemical Polishing Characteristics Of Titanium Alloy And Its DLC Coating

TC4 titanium alloy is currently the most widely used medical titanium alloy material,which has outstanding characteristics: low density(high strength coefficient),low modulus,corrosion resistance and better biocompatibility.Due to its own material properties,titanium alloy has low hardness and easy adhesion at the contact point during friction.The tribological properties are poor,which also leads to the adhesion of this material during chemical mechanical polishing.Phenomenon,polishing is difficult,and it is difficult to obtain a high-quality polished surface.In order to solve the above problems,the surface of TC4 titanium alloy was firstly modified by DLC coating.The friction characteristics,electrochemical corrosion characteristics and polishing characteristics of TC4 titanium alloy before and after surface modification were compared.The first is to simulate the polishing flow field,use Gambit to establish a two-dimensional flow field model,use fluent software to simulate the flow field,and analyze the factors such as ultrasonic cavitation,ultrasonic vibration frequency,ultrasonic vibration amplitude and polishing liquid film thickness under the test piece.The influence of flow field performance parameters such as absolute pressure,flow rate and gas holdup of flow field.It is concluded from the simulation results that the cavitation is mainly concentrated on the lower surface of the test piece,and the cavitation makes the parameters such as the absolute pressure,velocity and gas holdup of the flow field on the test piece evenly distributed,and obtains better flow field performance;ultrasonic vibration The increase of frequency and amplitude can enhance the mechanical removal effect.The ultrasonic vibration frequency and amplitude should be reasonably selected according to the actual polishing condition;the thickness of the polishing liquid under the test piece should preferably be greater than 1 mm,so that the effect of ultrasonic cavitation can be fully exerted.The flow field performance of the test piece is kept consistent,and the flow field performance is better,and the surface polishing quality of the test piece is improved.Then the 3D simulation model is built for simulation,and the experimental results are verified to prove that the simulation results are reliable.Then,the DLC coating experiment was carried out on the surface of TC4 specimens by bias-controlled cage-shaped hollow cathode discharge.The surface morphology,film thickness,hardness and film-bonding force of the DLC film were tested.It was found that the DLC coating could be greatly improved.The hardness of the TC4 matrix;the film-based bond strength of the DLC film is between HF3 and HF4,within acceptable levels.After the friction and wear and electrochemical experiments on the TC4 specimens before and after DLC coating,it was found that under the three friction conditions of dry friction,water lubrication and oil lubrication,the DLC coatings showed excellent wear reduction and can also be used for the counter grinding.The part has a good protection.The DLC coating can greatly improve the friction characteristics of the TC4 substrate.In addition,the DLC coating can greatly improve the corrosion resistance of the TC4 substrate.Finally,polishing experiments were carried out on TC4 and DLC coated specimens.Ultrasonic vibration electrochemical mechanical polishing tester was used to test the polishing parameters of polishing pad,abrasive grain,polishing solution,polishing pressure,polishing voltage and ultrasonic vibration.The influence of polishing parameters on material removal rate and surface quality,and finally the corresponding optimal polishing parameters.It has been found that surface DLC coating treatment of TC4 specimens can improve the polishing characteristics and make it easier to obtain a high-quality polished surface.