Research On Sapphire Magnetorheological Finishing Fluids

Sapphire is a kind of the high hardness oxide, whose hardness is second only to diamond. With many excellent characteristics, such as good stability, pervious to light, wear resistance, and lectromagnetic insulation, it has been widely used in the fields of scientific research, industry and national defense, especially the aerospace and military. However, the available processing methods are difficult to meet the demand of the sapphire. Magnetorheological finishing (MRF) is a new type of optical manufacturing technology, which processes many advantages, like the high efficiency, good surface quality of machining and computer controllability. Therefore, this paper is mainly about the MRF fluid of the sapphire on the ring type MRF machine.In this thesis, the removal mechanism of MRF fluid of sapphire was analyzed, and the formulation research of the MRF liquid and optimization analysis of the experiment were carried out to improve the removal rate of the MRF fluid and reduce the surface roughness of the sapphire.Firstly, the chemical corrosion test on the sapphire is applied to verify the alkaline environment of sapphire, providing a reference basis for the subsequent experiments. Then, the composition and function of the main ingredients in the polishing liquid were researched. The choice experiment of the components of the polishing fluid is performed on the fine grinding polishing machine. The suitable polishing abrasive, pH regulator, additives and other main ingredients were selected though the above experiments. Finally, the polishing liquid obtained by single factor experiment combined with magnetorheological liquid, the experiment of the MRF process on the sapphire is carried out on the ring type MRF machine. The optimum process parameters are obtained by the orthogonal test, which is mainly about the influence on the polishing effect of each component from the MRF fluid. The experimental results show that: the surface roughness Ra of the sapphire is 308.4 nm after the fine grinding process by the W5 micro diamond powder; while the Ra is 48.38nm by the MRF process, indicating that the MRF fluid can be used in sapphire. Finally, the formulation of the sapphire MRF fluid is determined.