Study On Lubrication Performance Of Magnetic Fluid With Magnetic Surface Texture

Magnetic fluid (MF) is a new magnetic function material, which can be magnetized as soft magnet and still possesses flowability of fluid at the same time. Lubrication is an important application of magnetic fluid. When serving as lubricant, MF can be retained at the friction zone with an external magnetic field and hence improve the lubrication effect. Moreover, with a designed magnetic field the lubricant can be prevented from leaking and increase the load capacity of lubricant film. Considering the above advantages, the tribological performance of MF and the design of magnetic field for its lubrication were studied.The static supporting capacity and lubrication performance of MF were firstly studied with an external magnetic field applied. Aiming at MF lubrication, the design of magnetic surface texture was proposed, which contains both geometric surface texture and effects of magnetic field. Magnetic surface textures were created on metal surface using micro-electrochemical machining and electrodepositing. Then friction and wear tests were conducted with a pin-on-disk test rig. The effects of magnetic surface textures on tribological behavior under the lubrication of MF were investigated by comparing with untextured surfaces lubricated by carrier liquid and MF and normal textured surface lubricated by MF. Finally, the optimization of the design of MF lubricated magnetic surface texture was conducted by choosing appropriate MF and geometric parameters of texture. And the effects of MF's saturation magnetization (Ms) and texture's area ratio on tribological performance were analyzed. The main research results are as follows:(1) Under external magnetic field MF has static supporting capacity and the supporting capacity increases with the increase of its Ms. With an external magnetic field applied, significant improvements in antifriction and wear resistance were obtained by using MF with proper Ms as lubricants.(2) Magnetic surface textures can be fabricated on metal surface by using photolithograph, micro-electrochemical machining and electroplating. When lubricated with MF, magnetic surface texture was observed to be conducive to form effective lubrication at low sliding velocity, which can reduce the friction and wear efficiently. On the other hand, magnetic surface texture can increase the friction at high sliding velocity when lubricated by MF under the present test conditions.(3) MF's saturation magnetization and texture's area ratio will affect the tribological performance. Considering the test results in all speed-load conditions, 16kA/m MF is an appropriate lubrication and the best range of surface texture's area ratio is 5%~10%.