Study On The Polishing Technology Of CVD Diamond Film In The Inner Hole Of The Drawing Die

CVD diamond-coated drawing dies have surface finish of natural diamond dies, wear resistance of polycrystalline diamond dies and swelling resistance of cemented carbides dies, which are becoming a new generation of highly competitive drawing die. So far, however, related research about polishing the hole of CVD diamond-coated drawing dies have not been reported.This paper has carried out polishing technology research about CVD diamond film on the inner hole of the drawing dies. The main contents have three parts, including device development, mechanical polishing process research and chemical mechanical polishing process research. Specific research contents and conclusions are as follows:1. On the basis of research on special polishing device, adopting the modularity design theory, the die clamp and its transmission module, the polishing head and its transmission module have been designed, electromagnetic induction heating module, polishing device bed module. processing and purchasing the required parts for assembly and debugging, successful develop the specific polishing device for CVD diamond film on drawing dies inner hole.2. Research on the mechanical polishing process, the result shows that, using self-made polishing head that containing different diamond particles in turn to process rough polishing and semi-finished polishing on diamond coating. Ra is falling fast in the initial polishing stage, subsequent decline slower, and flatten out. As the die rotation speed increase appropriately, micro-cutting times of coating cutted by diamond polishing head in unit time will increase, so the raised peak in the coating surface can be polished faster, improving the efficiency of polishing. Appropriate increase the polishing load, then the grain on the coating surface will be subject to bigger shear force, which makes the grain easier to break and fall off, also improving the efficiency of polishing. With the optimal mechanical polishing process, initial roughness of diamond coated is 4.1 um, after 1.5h of rough polishing and 3h semi-finished polishing, the surface roughness can reach to 0.085 um.3. Research on the chemical mechanical polishing process, the result shows that, proceeding chemical mechanical polishing on diamond coating with boron carbide and tungsten-copper carbide alloy compound polishing head respectively, the high hardness boron-copper carbide alloy compound polishing head have high polishing efficiency. Properly increasing the dies temperature can quicken graphite catalysis process of diamond coating, improve the efficiency of polishing, but high temperature could weaken the mechanical function of chemical mechanical polishing. With the optimal chemical mechanical polishing process, initial roughness of diamond coating is 0.085 um, after 4h of chemical mechanical polishing, the surface roughness can reach to0.028 um.