The effects of deposition parameters on the grain morphology and wear mechanism of monolayer diamond grinding tools fabricated by hot filament CVD method

摘要

The hot filament chemical vapor deposition technique (HFCVD) is used to fabricate monolayer grinding tools with high quality diamond abrasive grains. The high pressure and high temperature (HPHT) diamond seeds are distributed on SiC substrate randomly by a spin coater machine. Then epitaxial growth of CVD diamonds is conducted on both seeds and substrate simultaneously. The heteroepitaxial diamond film on substrate serves as a bonding layer to anchor the seeds, and the homoepitaxial growth of the seeds leads to changes in their morphology, purity, as well as mechanical properties. The grown seeds can be used as abrasive grains of the grinding tools. In this work, a systematic study is presented into the effects of deposition parameters (substrate temperature, carbon concentration, reactive pressure, bias current) on the growth behavior of diamond seeds. As a result, it is found that the well-faceted single crystal diamond (SCD) grains can be grown at 800 degrees C, 4.5 KPa, carbon concentration of 1.5% and bias current of 2 A. Besides, the increase of temperature and decrease of pressure allow the changes from SCD grains to microcrystalline diamond (MCD) clusters or further, to nano crystalline diamond (NCD) clusters, while the high bias current and carbon concentration promote the growth of dislocated planes and secondary nucleation. Moreover, it is found that the protrusion of the diamond abrasives can be controlled by the difference in growth rates between seeds and diamond bonding films under various conditions. Finally, the wear resistance of diamond grains is tested. Results show that the wear of SCD grains is dominated by a high rate of wear flat and few fractures, and the wear of MCD grains exhibits less wear flat but more fractures, while the NCD grains exhibit the worst wear resistance in terms of both fracture and wear flat.