| Diamond has excellent properties in mechanical, optical, electrical, thermal, acoustic and chemical stability. Single crystal diamond is an ideal material for manufacturing cutting tools, semiconductor electronic devices, high power laser window, acoustic wave filter and wearing resistance coating components because of excellent physical and chemical properties. With the improvement of synthetic diamond technology, the diamond production of world is more than 4.6 billion carats every year, and various properties of synthetic diamond have been developed and utilized. At present, because the artificial diamond can’t directly meet application requirements in shape and quality of surface, and must be grinded or polished before being used. But because of excellent physical and chemical properties, manufacturing processing of single crystal diamond is very difficult.Dynamic friction polishing technology can ensure accuracy and efficiency of diamond processing, and only needs simple equipment. This paper selects this processing technology to polish single crystal diamond, and uses WMoCr plates to research polishing processing and theory of polishing. The main research contents and conclusions are as follows:(1) The micro WMoCr composite powder prepared by mechanical alloying is used as original material. Through controlling hot pressing sintering process, the effects of sintering temperature, pressure, holding time on the density, hardness and micro structure of the alloy materials were investigated. The results show that WMoCr alloy materials with high density and high hardness can be prepared by the method of mechanical alloying combining with hot pressing solid phase sintering. The materials with high density are fabricated under processing conditions of sintering temperature of 1400℃, pressure of 30 MPa and holding time of 30 min. The relative density of materials is 96.49%, and the hardness is 777.78HV.(2) High-performance WMoCr alloy materials are prepared by mechanical alloying and hot pressing solid phase sintering. By means of WMoCr polishing plates, polishing parameters of DFP single crystal diamond are studied. Single crystal diamonds are polished for 20 min under different polishing pressures and polishing speeds. Through investigating the removal rate and surface quality of the diamond, the wear amount of pads and the degree of oxidation to formulate reasonable polishing parameters. The results show that performance of WMoCr pads are good. The removal rate of diamond is 2.3 um/min under low polishing parameters 5.67 MPa and 8.38 m/s, and the surface quality of the diamond, the wear amount and oxidation of pads are better controlled.(3) Based on analysis of single crystal diamond surface morphology, we establish a geometric structure model which has four squaretable micro convex on surface, considering the contact and friction properties of the polishing process to calculate heat flux density, the heat flux distribution coefficient and air convection coefficient and so on. Under polishing parameters of polishing pressure 80 N and polishing speed 8000 r/min, ANSYS thermal analysis software is used to finish friction temperature field simulation for dynamic friction polishing process of single crystal diamond. The simulation results correspond with the experiment. It shows that the simulation model is ideal.(4) Through analysis of the relationship between diamond polishing measuring temperature and its removal rate, critical polishing parameters of diamond polishing surface graphitization are obtained, which are 6000 r/min and 65 N. Then, the thermal analysis software ANSYS is used to solve the diamond temperature field under the diamond polishing parameters, and calculate the whole range of diamond temperature distribution. Results show the lowest critical value of diamond graphitization temperature is between 624.5～658.1℃. |
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