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In order to improve the processing accuracy of silicon nitride ceramic balls and to investigate the mechanism of forming ceramic balls by flexible support grinding method, a new cone-type flexible support grinding method with controlled deflection motion of grinding disc is proposed. Based on the new grinding method, a simulation model is established to deeply analyze the influence of the deflection motion of the grinding disc on the grinding trajectory and force state of the silicon nitride ceramic balls. Orthogonal experiments were conducted on a new cone-type flexible support grinding platform built to further analyze the effect of grinding disc motion characteristics on ball formation. Simulation and experimental results show that under the flexible support grinding method, As the increases of grinding disc deflection angle, the standard deviation of ball trajectory uniformity decreased from 43.58 to 35.49, the maximum contact force increased to 4 times the initial value, the average ball diameter variation increased from 1.466 μm to 2.382 μm, and the batch diameter variation increased from 4.98 μm to 10.27 μm. The lower grinding disc deflection motion is beneficial to optimize the grinding trajectory, but increases the unevenness of the ball force, which is not conducive to improving the average ball diameter variation and batch diameter variation of silicon nitride ceramic balls. In the actual process, the angle of deflection of the grinding disc must be controlled to within 0.02°.

In order to obtain the optimal process parameter combination of double-sided grinding Si3N4 cylindrical rollers, the orthogonal experiment method was used to explore the influences of the grinding disc speeds, the grinding pressures and the basic particle sizes of the abrasive particles on the surface quality and the removal efficiency of Si3N4 cylindrical rollers. The results of the surface roughness and the material removal efficiency of the specimen are taken as the basis for optimizing the grinding process parameters. The results show that the surface roughness of the specimen first decreases and then increases with the increase of the grinding disc pressure and the grinding speed. The basic particle sizes of the abrasive are positively correlated with the surface roughness of the specimen, while the grinding disc speed and the grinding pressure are positively correlated with the removal efficiency. The optimum combination of grinding parameters for Si3N4 cylindrical rollers is that the basic particle size of diamond abrasive is 2.6 μm, the grinding disc speed is 20 r/min and the grinding pressure is 0.15 MPa. Under the optimal parameters, the smooth and undamaged Si3N4 cylindrical rollers with surface roughness of 0.0486 μm and removal efficiency of 1.20 μm/min can be obtained.

Micro-diamond film, nano-diamond film and diamond-graphite composite film were deposited on silicon carbide substrate by hot filament chemical vapor deposition. The surface morphology and phase of the grown diamond films were analyzed using scanning electron microscope, atomic force microscope and Raman spectrometer. The friction coefficient and the wear rate of diamond films were measured by friction experiments. The friction and wear properties of diamond films were studied by comparing the experimental results. The results show that the diamond-graphite composite film has better friction and wear properties, the surface roughness of which is 53.8 nm. The friction coefficient (0.040) is similar to that of the nano-diamond film (0.037), while the wear rate is the lowest, 2.07×10−7 mm3·N−1·m−1. Compared with those of SiC substrate, the wear rate (9.89×10−5 mm3·N−1·m−1) and the friction coefficient (0.580) of the diamond films have been greatly improved, which indicates that depositing diamond on the surface of SiC substrate significantly improves the performance of the silicon carbide in the field of friction.