Investigation on Enhanced Machinability of SiC Ceramics through Photocatalytic Vibration Composite Polishing.

The problems of low polishing efficiency and serious surface damage in the processing of silicon carbide (SiC) ceramics are well-known. In view of the above problems, a new method of photocatalytic vibration composite polishing (PVCP) combined with a compound control strategy was proposed. A vibration-assisted device was developed, and a compound control system was designed for the device to improve the trajectory tracking accuracy. Experiments were carried out to verify the effectiveness of the vibration-assisted device and the compound control system. In addition, methyl orange degradation and fading experiments, redox potential measurement experiments, and SiC ceramic surface hardness characterization experiments were carried out to reveal the effects of vibration and photocatalytic parameters on polishing solution oxidation and SiC ceramic surface mechanical properties. Finally, the effects of photocatalysis, vibration frequency, amplitude, and the compound control system on the polishing effect were analyzed. The results show that when the UV intensity is 100%, the polishing force is 3-4N, the vibration frequency is 400 Hz, the amplitude is 15 µm, and the surface roughness of SiC ceramics is reduced by about 11 nm after the introduction of the compound control system, which verifies the effectiveness of the combination of the compound control system and PVCP.

Analytical Prediction of Subsurface Damages and Surface Quality in Vibration-Assisted Polishing Process of Silicon Carbide Ceramics.

Subsurface damages and surface roughness are two significant parameters which determine the performance of silicon carbide (SiC) ceramics. Subsurface damages (SSD) induced by conventional polishing could seriously affect the service life of the workpiece. To address this problem, vibration-assisted polishing (VAP) was developed to machine hard and brittle materials, because the vibration-assisted machine (VAM) can increase the critical cutting depth to improve the surface integrity of materials. In this paper, a two-dimensional (2D) VAM system is used to polish SiC ceramics. Moreover, a theoretical SSD model is constructed to predict the SSD. Furthermore, finite element simulation (FEM) is adopted to analyze the effects of different VAP parameters on SSD. Finally, a series of scratches and VAP experiments are conducted on the independent precision polishing machine to investigate the effects of polishing parameters on brittle-ductile transition and SSD.

Subsurface Damage in Polishing Process of Silicon Carbide Ceramic.

Subsurface damage (SSD) in the polishing process of silicon carbide (SiC) ceramic presents one of the most significant challenges for practical applications. In this study, the theoretical models of SSD depth are established on the basis of the material removal mechanism and indentation fracture mechanics in the SiC ceramic polishing process. In addition, the three-dimensional (3D) models of single grit polishing are also developed by using the finite element simulation; thereby, the dynamic effects of different process parameters on SSD depth are analyzed. The results demonstrate that the material removal was mainly in brittle mode when the cutting depth was larger than the critical depth of the brittle material. The SSD depth increased as the polishing depth and abrasive grain size increased, and decreased with respect to the increase in polishing speed. The experimental results suggested a good agreement with the theoretical simulation results in terms of SSD depth as a function of polishing depth, spindle speed, and abrasive grain size. This study provides a mechanistic insight into the dependence of SSD on key operational parameters in the polishing process of SiC ceramic.