| Titanium alloy has many advantages such as high strength,low density,high temperature resistance,good corrosion resistance and good biocompatibility,and is favored by aerospace,shipbuilding,chemical and medical industries,among which titanium(Ti-6A1-4V)Alloy as the representative.However,poor wear resistance of titanium alloys in practical applications,easy to wear and tear limits its application.This topic is intended to use micro-arc oxidation technology to improve the wear resistance of titanium alloysAs the electrolyte and electrical parameters on the performance of micro-arc oxidation film plays a key role.On the one hand,we can change the electrolyte to change the composition of the coating to increasing the hardness of the coating itself and the abrasive resistance.On the other hand,we can adjust the coating thickness by adjusting the electrical parameters of micro arc oxidation to make it have appropriate thickness,and at the same time minimize the surface.roughness of the ceramic coating.The experiment was carried out under constant voltage.TC4 titanium alloy was treated by micro arc oxidation in solution of P-Al-Zr system,P-AI-W and P-Ti system.First,The optimization experiments of each electrolyte system were carried out to obtian the relative optimal system of each solution Then in the optimized electrolyte system to determine the corresponding relative optimal electrical parameters,The effects of electrical parameters(voltage,duty cycle,frequency and oxidation time)on the film thickness,surface roughness,surface topography and phase structure were studied.Finally,a micro-arc oxidation coating was prepared on the surface of TC4 titanium alloy on the basis of the above two parts.The friction and wear properties of MAO film were measured by HSR-2M high speed reciprocating friction and wear tester.Experimental results show that:Within a certain range,the growth rate and surface quality of MAO coatings prepared by three different electrolyte systems are related to the micro-arc oxidation parameters including pulse voltage,frequency,duty cycle and oxidation time.In the constant voltage power supply mode,increasing the pulse voltage and the duty ratio will increase the growth rate of the film,the coating thickens and the pore diameter of the surface is larger,and the oxide film becomes more rough;With the change of frequency and oxidation time,there is no regularity in the change of film thickness and surface roughness,indicating that each electrolyte system has its corresponding range of electrical parameters.The ceramic coating prepared by P-Al-Zr and Al-P-W electrolyte is mainly composed of Al2TiO5 and rutile TiO2.This is due to its two main film-forming salt((NaPO3)6 and NaAlO2).However,the micro-arc oxidation film prepared by P-Ti electrolyte system is mainly composed of anatase TiO2 and rutile TiO2.The main film forming electrolyte of the electrolyte system is the difference between the sodium hexametaphosphate and the former two It can be seen that the main film forming salt in the electrolyte system plays a key role in the microstructure of the ceramic coating.In addition,The electrical parameters have a certain influence on the phase composition of MAO coatings,because the change of the electrical parameters will cause the change of the heat released during the micro-arc oxidation process,thereby affecting the thickness and temperature of the micro-arc oxidation film,Which in turn affects the thickness and temperature of the micro-arc oxide film.The TC4 titanium alloy was micro-arc oxidized in the optimized P-Al-Zr electrolyte,P-Al-W electrolyte and P-Ti electrolyte.Under the condition of 1.2 N dry friction,the friction coefficient of the three kinds of micro-arc oxidation coating and bearing steel ball on the mill relative to the TC4 titanium alloy substrate and the bearing steel ball on the wear reduction,TC4 titanium alloy wear resistance Has been improved.Under the conditions of oil friction of 1.2 N and 3.2 N,the friction coefficient of the micro-arc oxidation coating prepared by the above three electrolyte systems is greatly reduced compared with that of the TC4 titanium alloy and the bearing steel balls,And the coefficient of friction jump smaller and stable.It shows that the micro-arc oxidation coatings prepared by the three kinds of electrolyte electrolytes all show excellent lubricating and frictional properties And it can be seen that the micro-arc oxidation coating prepared in the P-Al-W electrolyte system is better and more wear-resistant than the micro-arc oxidation film prepared in the other two electrolyte systems. |
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