| The preparation technique of man-made diamond film especially the large size chemical vapor deposition (CVD) thick diamond film has greatly developed these years. Diamond film has been applied from the tranditional areas of cutter and mould to the high-tech fields such as high frequency communication and photoelectricity, so the standards of processing accurity and surface quality requires much higher. However, diamond film is very difficult to process since its characteristics of high hardness and high chemical inertness. Although there have already been some kinds of diamond film polishing techniques, they can not meet the requiments of high efficiency and low cost. Relatively lagged diamond film polishing techniques are becoming the main barriers for the wide spread applicatin of diamond film.Dynamic friction polishing is a new polishing technique which can realize fast polish by the complex friction-thermochemistry effect in processing area. It enables the processing area to achieve the transition temperature (usually 600-800℃) of diamond to graphite in atmosphere, by the high-speed friction effect between polishing plate and diamond film. This polishing technique is very promising because it neither requires vacuum or sealed atmosphere nor needs heating equipment, not even needs the expensive polishing equipment. Materials containing iron element such as stainless steel or cast iron are normally used to make polishing plate in order to ensure polishing plate's strong catalytic ability on diamond, however, these materials can hardly adapt to polishing environment such as high temperature and high-speed friction. In that case, the polishing plate is easily worn out which seriously affect the polishing precision, what's worse is that polishing plate gets sharp plastic deformation and the deformed material adheres to the diamond surface, which leads to the drop of the polishing efficience and polishing quality. Therefore, it is urgent to develop a new type of polishing plate material with the quality of high-temperature wear resistance and strong catalytic graphitization ability on diamond. In addition, efficient removal can only be realize with the processing area achieving the transition temperature of diamond to graphite, and with the help of the composite action of friction-thermochemistry during the diamond film processing. However, if the temperature is too high, it would lead to the sharp decline of polishing plate's hardness and wear resistance, which results in low processing efficiency and precision, what's worse is that the too high temperature even leads to the extreme graphitization and overall oxidation. In that case, calculation and control of temperatures field in the processing area are key for efficient and high-precision processing, however, the calculation of the temperature field during the dynamic friction polishing is extremely difficult because it can be affected by combined effects of many factors such as polishing rotation rate, polishing pressure, and polishing system's thermal conductivity.A new type of polishing plate material—FeAl based alloy, was developed by the technology of combining high-energy ball-milling and hot-pressing sintering, aiming at solving the problems of existing in dynamic friction polishing techniques mentioned above, and the performances of the polishing plate material were optimised by doping rare earths. Diamond film's temperature field during dynamic friction polishing process was simulatd with the help of ANSYS simulation software, and the reasonable parameters for diamond films dynamic friction polishing was obtained based on the simulation. Diamond films were polished by dynamic friction method with stainless steel 304 (abbreviated as SS304) polishing plate and self-made FeAl-based alloy polishing plate respectively, and the polishing effect of these two kinds of polishing plates was compared. Dynamic frictional polishing process and mechanism using FeAl based alloy polishing plate were also analyzed. The main research contents include:(1) According to the principles and characteristics of the dynamic friction polishing technology, we chose FeAl based alloy which has the quality of abnormal temperature-strength, excellent wear resistance and catalytic graphitization ability on diamond as polishing plate material. We further prepared sintered FeAl based alloys with different content of rare earth using high-energy ball milling and hot-press sintering technique, and analyzed the effect of milling time and rare earth content on the sintered alloy's structure, density, hardness, flexural strength, oxidation resistance and high temperature wear resistance. The results showed that the FeAl based alloy which is made of Fe and Al mixed powder doped 1wt.% rare earth, ball-milled for 60 hours and sintered for 1 hour in Vacuum at 1200℃under the stress of 30MPa has the best combination property.(2) Diamond film was polished by using the self-made FeAl based alloy plate under different temperature at the atmosphere, and the influence of polishing temperature on the wear situation of FeAl based alloys as well as the polishing effect on diamond film was also analyzed. The results showed that the ideal temperature range for FeAl based alloys polishing diamond film is 650～700℃.(3) A quadrangular frustum pyramid model of the diamond asperity was built based on the diamond film surface topography before and after polishing, and the temperature field of diamond film during the dynamic friction polishing was simulated with the help of ANSYS thermal analysis software. Based on the simulation, we concluded that the best parameters of FeAl based alloy plate polishing diamond film are as follows:polishing pressure 80N (5MPa), polishing speed 1440r/min (10.25m/s).(4) We compared the polishing effects of two kind of polishing plates, one of which is made of SS304 and the other is made of our self-made FeAl based alloy, by doing dynamic friction polishing on diamond film. The polishing mechanism of using FeAl alloy polishing plate was also analyzed. The results showed that with FeAl alloy as the material the removal rate of diamond film can be 7.89mm3/h which is 68% higher than that with SS304, the wear rate of FeAl alloy polishing plate is only 15% of that of SS304. The polishing mechanism is: under the combined action of friction heat and iron catalyst, a soft, easily oxidized and fast diffusible graphite phase formed on the asperities of diamond film by the graphite transition, then the graphic phase was removed under the combined action of mechanical action, oxidation and diffusion.
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