Characteristics: High temperature, corrosion resistance, acid and alkali resistant silicon nitride ceramic balls are precision ceramics sintered in a high temperature in a non-oxidizing atmosphere. Used and has good performance of insulation and magnetism. At 800 ° C, the strength and hardness are almost unchanged, and its density is 3.20g / cm3, which is almost 1/3 of the weight of bearing steel. The centrifugal force is small during rotation. High-speed operation can be achieved. It is also self-lubricating, and it can be used in environments with high pollution without lubricant. Become a ceramic bearing, the preferred material for hybrid ceramic ball bearings. Silicon carbide ceramic balls have a density of 3.20 g / cm3 and Si3N4 balls. At 1400 ° C, the strength and hardness are almost unchanged. Pollution caused by the lubricating medium has higher hardness than Si3N4, but lower compressive strength and fracture toughness than Si3N4. Zirconia ceramic balls have high strength and toughness at normal temperature, good wear resistance, high temperature and corrosion resistance, high rigidity, non-magnetic permeability, and electrical insulation. At 600 ° C, the zirconia ceramic ball has almost the same strength and hardness. Its density is 6.00g / cm3. If the thermal expansion rate is close to that of metal, it can be used in conjunction with metal.