Ultra-smooth and low-damage processing of single-crystalline 4H-SiC has become a research focus as a substrate for third-generation semiconductor wafers. However, the high hardness and strong chemical inertia significantly affect 4H-SiC chemical-mechanical polishing (CMP) efficiency and accuracy. In this study, polishing process optimization experiments of 4H-SiC are conducted based on the grey relational analysis method to achieve low surface roughness (Ra) and high material removal rate (MRR). First, MRR and Ra of Si surface (0001) are obtained by orthogonal experiments considering down force, rotation speed, slurry flow rate and abrasive particle size as four key factors. Then the grey relational coefficient and grey relational grade of MRR and Ra are calculated by data processing. The results show that significant factors of the single-objective process are rotation speed, down force, particle size, and flow rate, while the factors of the multi-objective process are down force, flow rate, rotation speed, and particle size in turn. Finally, the MRR of 208.12 nm/h and Ra of 0.391 nm are polished using multi-objective optimization process parameters. The polishing efficiency and accuracy were improved, confirming the applicability of grey relational analysis in CMP.

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Polishing determines the final surface quality of the aero engine, which have great influence on its working performance and working life. By analyzing the structure and working principle of the flexible self-adaptive polishing platform of the blisk, the abrasive cutting model of the flap disc is established. The theoretical calculation of the effect of elastic deformation during the polishing process on the contact length of flap disc and blisk. The model of polishing force, polishing heat and temperature field during the polishing process of the flap disc are established and analyzed. Single factor method is used to analyze the influence of process parameters on polishing force, polishing temperature, roughness and specific polishing energy. Finally, the polishing test shows that the optimized process parameters improve the polished surface quality and meet the requirements of the blade polishing process.