Preparation And Tribological Properties Of Porous Anodic Alumina Self-lubricating Thin Films

Aluminum and its alloys have been widely used in recent years due to their excellent mechanical properties.Anodic oxidation is the most widely used surface modification technology for aluminum and its alloys at present.In this paper,the preparation technology of PAA membrane with large interpore distance and the deposition process of MoS2 composite self-lubricating film were studied systematically with aluminum as the main material.The main research contents include the following aspects:The PAA film is prepared using the two step oxidation method.The first step is to prepare a regular PAA film in oxalic acid by rising the voltage slowly.And the micropores need to be retained in the bottom after first step oxidation.In the second step,the high voltage was conducted directly in the phosphoric acid to get the PAA membrane that can be directly used on the membrane surface.By studying the influence of main factors such as heat dissipation and solution concentration,the membrane preparation process was optimized.After studying the surface morphology,it was found that the interpore distance changed with oxidation voltage.The interpore distance increases by 28.7 nm when the voltage increases 10V.Under the condition of 35? and 5%phosphoric acid solution,the average pore size increased by 24.16nm for ten minutes.By means of ultrasonic deposition and electrophoretic deposition,MoS₂self-lubricating thin films were prepared on the surface of PAA film.It was found that electrophoretic deposition has better preparation effect.The mechanical properties of PAA films were tested.It was found that the hardness of the PAA film decreased with the increase of pore size and interpore distance.The wear resistance of PAA films with different morphology was tested.It was found that the friction coefficient decreased with the diameter of the pore increases.When the porosity was fixed,the wear resistance of the membrane increased first and then decreased with the increase of interpore diastance.The wear resistance of the composite film was best when the interpore distance was 280nm.The corrosion resistance of PAA films prepared by different processes was tested.It was found that the PAA films can effectively improve the corrosion resistance of Al.The PAA films have better corrosion resistance due to low porosity,and the corrosion resistance is generally poor when the porosity is large.After enlarging the pore,the corrosion resistance of PAA film decreases sharply,even worse than the corrosion resistance of pure Al.However,the deposition of MoS₂ in the pores can improve the corrosion resistance of the PAA film.