Ceramic mirror polishing requires selecting the appropriate polishing slurry system based on the ceramic material, mirror surface roughness requirements, and process stage. The mainstream categories are cerium oxide, alumina, and diamond.
Polishing Slurry Selection Based on Ceramic Material:
Cerium oxide polishing slurries are currently the most widely used category in industrial ceramic mirror polishing. With a Mohs hardness of approximately 6.5-7, they match the hardness of most industrial ceramics (alumina ceramics, zirconia ceramics), effectively removing machining marks without excessively scratching the workpiece surface. Water-based cerium oxide polishing slurries contain dispersants and stabilizers, ensuring uniform particle dispersion and easy cleaning of residue after polishing. They are suitable for mirror surface roughness requirements of Ra 0.01-0.08.
Alumina polishing slurries have a Mohs hardness of approximately 9 and stronger grinding ability than cerium oxide slurries. They are suitable for the semi-finishing polishing stage of high-hardness ceramics such as silicon nitride and silicon carbide ceramics. They can quickly remove machining allowances and tool marks after rough machining, and can then be combined with cerium oxide polishing slurries to complete the fine polishing process. Some oil-based alumina polishing slurries can be used in batch processing scenarios with high rust prevention requirements. Diamond-based polishing slurries, with a Mohs hardness of 10, are currently the most powerful type of polishing slurry. They are suitable for ultra-precision mirror polishing of superhard ceramics such as boron carbide and cubic boron nitride, achieving a mirror finish with a roughness of Ra 0.005 or less. However, they are expensive and are only used for high-precision optical and military-grade ceramic component processing.
Selection based on polishing process stage:
Rough polishing: Use alumina or diamond polishing slurry with a particle size of W10~W20 to quickly remove turning and grinding allowances and deep tool marks from the workpiece surface.
Semi-fine polishing: Use alumina polishing slurry with a particle size of W3~W10 to refine the workpiece surface roughness to Ra 0.1~0.8.
Fine polishing/mirror finish: Use cerium oxide polishing slurry with a particle size of W0.5~W3 to improve the roughness to Ra 0.01~0.08. For ultra-precision mirror finish applications, use nano-diamond polishing slurry with a particle size of W 0.1 or less, combined with chemical mechanical polishing.
Final Processing Completion Selection and Practical Considerations
Matching Polishing Equipment Type: Surface polishing machines mostly use water-based polishing fluids, while vibratory polishing machines can be paired with oil-based polishing fluids to reduce workpiece impact.
Dilution Ratio Must Strictly Follow the Product Instructions: Most polishing fluids need to be diluted with water at a ratio of 5% to 10% by weight. Too high a concentration will cause surface scratches, while too low a concentration will reduce polishing efficiency.
Mismatch Risk Avoidance: Zirconia ceramics should not be polished with high-hardness, coarse-grained diamond polishing fluids, as this can easily cause irreversible scratches; silicon carbide ceramics should avoid using excessively fine-grained cerium oxide polishing fluids, as this will result in insufficient grinding efficiency.